Practice with free quizzes and labs

Ten Neuroscience and the Nervous System questions on signaling and evidence, with a travel-time calculation. Every answer is explained.

About 12 minutes.

10 questions.

Ten Plant Biology questions cover transport, growth, and reproduction, with a growth-rate calculation. Every answer is explained.

About 12 minutes.

10 questions.

Evolution in Biology: ten practice questions on allele calculations and evolutionary mechanisms. Every answer is explained.

About 12 minutes.

10 questions.

Change genotype fitness and starting allele frequency to follow selection with random mating in an illustrative population.

About 10 minutes.

Cell Biology: ten questions on membranes, organelles, and division, including an ideal cell-count calculation. Every answer is explained.

About 10 minutes.

10 questions.

Biotechnology: ten questions on DNA tools and biological processes. Includes calculations; answers explained.

About 10 minutes.

10 questions.

Ten Acids and Bases practice questions combine pH and neutralization calculations with concepts. Every answer is explained.

About 14 minutes.

10 questions.

Titrate a strong monoprotic acid with a strong base at 25 °C. Compare excess amounts, pH, and the equivalence volume.

About 8 minutes.

Environmental Chemistry in Practice: ten practice questions on concentration calculations and chemical fate. Every answer is explained.

About 12 minutes.

10 questions.

Electrochemistry: ten questions on cells, redox, and charge calculations. Every answer is explained.

About 11 minutes.

10 questions.

Periodic Table: ten questions on element boxes, trends, and particle calculations. Every answer is explained.

About 10 minutes.

10 questions.

Chemical Safety: ten conceptual questions on hazards, exposure controls, storage, and response. No calculations; every answer is explained.

About 10 minutes.

10 questions.

Chemical Reactions: ten questions on mass, mole ratios, and reaction patterns. Includes calculations; answers explained.

About 10 minutes.

10 questions.

Thermochemistry: ten practice questions on heat transfer and calorimetry, with concepts and calculations. Every answer is explained.

About 12 minutes.

10 questions.

Mix two samples in an insulated calorimeter model. Change materials, masses, and temperatures to compare equilibrium temperature and heat transfer.

About 8 minutes.

Chemical Bonding: ten conceptual practice questions on ions, electron sharing, and molecular shape. Every answer is explained.

About 12 minutes.

10 questions.

Solutions and Solubility: ten practice questions on concentration and dilution, with concepts and calculations. Every answer is explained.

About 12 minutes.

10 questions.

Calculate concentration with an ideal dilution model. Change solute mass and solution volume, compare presets, and solve preparation challenges.

About 8 minutes.

Ten Computer Vision practice questions cover calculations and concepts. Every answer is explained.

About 12 minutes.

10 questions.

Ten Context Engineering practice questions cover concepts and practical decisions. Every answer is explained.

About 12 minutes.

10 questions.

Debugging: Finding What Is Broken offers ten conceptual questions, with no calculations. Every answer is explained.

About 12 minutes.

10 questions.

Ten AI Coding Assistants questions test concepts about context, verification, permissions, and learning. No calculations. Every answer is explained.

About 12 minutes.

10 questions.

Agent Instruction Files: ten practice questions on scope, discovery, and checkable rules. Every answer is explained.

About 10 minutes.

10 questions.

Databases With AI: ten practice questions on retrieval concepts and a vector calculation. Every answer is explained.

About 12 minutes.

10 questions.

Binary Logic and Circuits: ten questions on binary numbers, gates, and hardware. Includes calculations; every answer is explained.

About 11 minutes.

10 questions.

Change binary inputs and compare gate outputs, a half adder, and complete truth tables.

About 8 minutes.

Sorting and Searching: ten questions on algorithms, search conditions, and operation counts. Includes calculations; answers explained.

About 11 minutes.

10 questions.

Internet: ten questions on packets, DNS, web requests, and security, including a transfer-time calculation. Every answer is explained.

About 10 minutes.

10 questions.

Data Structures: Lists, Trees, Maps: ten questions on storage choices and operation costs. Includes calculations; answers explained.

About 10 minutes.

10 questions.

Programming Fundamentals: Variables and Loops: ten questions on state, loops, and scope. Includes calculations; answers explained.

About 10 minutes.

10 questions.

Ten Capital Markets practice questions cover calculations and concepts. Every answer is explained.

About 13 minutes.

10 questions.

Ten Cost-Benefit Analysis practice questions cover calculations and concepts. Every answer is explained.

About 13 minutes.

10 questions.

Ten Inflation practice questions cover calculations and concepts. Every answer is explained.

About 14 minutes.

10 questions.

Ten Interest Rates practice questions cover calculations and concepts. Every answer is explained.

About 14 minutes.

10 questions.

Set a principal, nominal rate, compounding, and inflation. Compare balance growth with purchasing power and the exact real annual rate.

About 8 minutes.

Ten Globalization in the World Economy practice questions cover calculations and concepts. Every answer is explained.

About 12 minutes.

10 questions.

Ten Labor Markets practice questions cover calculations and concepts. Every answer is explained.

About 13 minutes.

10 questions.

Ten Opportunity Cost questions cover feasible alternatives and marginal choices, with production and cost calculations. Every answer is explained.

About 12 minutes.

10 questions.

Ten Income Distribution and Inequality questions cover measurement, work, and policy, with share and income calculations. Every answer is explained.

About 13 minutes.

10 questions.

Ten Subsidies questions cover incidence, incentives, and public cost, with equilibrium and benefit-split calculations. Every answer is explained.

About 14 minutes.

10 questions.

Change linear supply and demand and a seller subsidy. Compare buyer and seller gains, government cost, and deadweight loss.

About 8 minutes.

Public Goods: ten practice questions on benefit calculations and shared provision. Every answer is explained.

About 11 minutes.

10 questions.

Exchange Rates: ten practice questions on currency calculations and market mechanisms. Every answer is explained.

About 12 minutes.

10 questions.

Monopoly and Oligopoly: ten practice questions on market-power concepts and calculations. Every answer is explained.

About 14 minutes.

10 questions.

Compare illustrative monopoly and competitive outcomes for linear demand and constant marginal cost.

About 10 minutes.

Game Theory: ten questions on strategic choices, equilibria, and payoff calculations. Every answer is explained.

About 12 minutes.

10 questions.

Edit a two-player payoff matrix to find best responses, strict dominance, and pure-strategy Nash equilibria.

About 10 minutes.

National Debt: ten questions on debt, deficits, refinancing, and debt-ratio calculations. Every answer is explained.

About 10 minutes.

10 questions.

Change illustrative interest, growth, and primary balances to track a debt-to-GDP ratio and its steady-balance condition.

About 10 minutes.

Market Equilibrium: ten questions on equilibrium and shifts. Includes calculations; answers explained.

About 10 minutes.

10 questions.

Privatization: ten questions on ownership and regulation. Concepts, with every answer explained.

About 9 minutes.

10 questions.

Comparative Advantage: ten questions on opportunity cost and trade. Includes calculations; answers explained.

About 11 minutes.

10 questions.

Explore comparative advantage with two producers. Change daily output and terms of trade; compare opportunity costs, production frontiers, and specialization.

About 10 minutes.

Marginal Utility and Diminishing Returns: ten questions on utility and production, with concepts and calculations. Every answer is explained.

About 13 minutes.

10 questions.

Market Failure: ten practice questions on external costs, information, and public goods, with concepts and calculations. Every answer is explained.

About 15 minutes.

10 questions.

Adjust an illustrative external cost and per-unit tax. Compare market and efficient quantities, prices, tax revenue, external damage, and welfare loss.

About 9 minutes.

Productivity in Economics: ten practice questions on output per input and growth, with concepts and calculations. Every answer is explained.

About 12 minutes.

10 questions.

Shadow Economy: ten conceptual practice questions on hidden production, measurement, and incentives. Every answer is explained.

About 11 minutes.

10 questions.

Price Controls: ten practice questions on ceilings, floors, and market balance, with concepts and calculations. Every answer is explained.

About 12 minutes.

10 questions.

Explore a linear supply and demand model. Change prices and controls to see equilibrium, binding limits, shortages, and surpluses.

About 8 minutes.

Consumer Choice Theory: ten practice questions on budgets and utility, with concepts and calculations. Every answer is explained.

About 12 minutes.

10 questions.

Ten Urban Heat Islands practice questions cover calculations and concepts. Every answer is explained.

About 12 minutes.

10 questions.

Ten Pollution in Geography practice questions cover calculations and concepts. Every answer is explained.

About 12 minutes.

10 questions.

Ten Arctic and Antarctic Geography practice questions cover calculations and concepts. Every answer is explained.

About 12 minutes.

10 questions.

Ten Biodiversity Hotspots practice questions cover calculations and concepts. Every answer is explained.

About 12 minutes.

10 questions.

Ten Deforestation and Forest Change practice questions cover calculations and concepts. Every answer is explained.

About 12 minutes.

10 questions.

Ten Ecosystems and Biomes practice questions cover calculations and concepts. Every answer is explained.

About 12 minutes.

10 questions.

Ten Waste Management questions cover collection, treatment, and recovery, with rate calculations. Every answer is explained.

About 12 minutes.

10 questions.

Ten Migration in Human Geography questions cover movement, measurement, and impacts, with net-flow and rate calculations. Every answer is explained.

About 12 minutes.

10 questions.

Ten Water Scarcity questions cover supply, access, and allocation, with per-person and water-balance calculations. Every answer is explained.

About 12 minutes.

10 questions.

Ten Natural Resource Conflicts questions cover access, institutions, and shared resources, with a flow-share calculation. Every answer is explained.

About 12 minutes.

10 questions.

Food Security: ten practice questions on household calculations and the four dimensions. Every answer is explained.

About 11 minutes.

10 questions.

Marine Geography: ten practice questions on ocean processes and a distance calculation. Every answer is explained.

About 11 minutes.

10 questions.

Population Distribution and Density: ten practice questions on density calculations and population maps. Every answer is explained.

About 12 minutes.

10 questions.

Trade Routes: ten practice questions on route calculations and freight decisions. Every answer is explained.

About 11 minutes.

10 questions.

Transportation Networks: ten questions on routes, access, and network calculations. Every answer is explained.

About 10 minutes.

10 questions.

Conservation in Geography: ten questions on habitats, protection, and outcomes, including percentage change. Every answer is explained.

About 10 minutes.

10 questions.

Political Geography: ten conceptual questions on states, boundaries, jurisdiction, and maps. No calculations; every answer is explained.

About 10 minutes.

10 questions.

Renewable and Non-Renewable Resources: ten questions on renewal, stocks, and use. Includes calculations; answers explained.

About 9 minutes.

10 questions.

Tourism Geography: ten questions on visitor flows and local impacts. Includes calculations; answers explained.

About 9 minutes.

10 questions.

Energy Geography: ten practice questions on energy systems and capacity factor, with concepts and calculations. Every answer is explained.

About 11 minutes.

10 questions.

Global Supply Chains: ten conceptual practice questions on location, logistics, inventory, and disruption. Every answer is explained.

About 10 minutes.

10 questions.

Settlement Patterns: ten practice questions on settlement forms and density, with concepts and calculations. Every answer is explained.

About 11 minutes.

10 questions.

Topography and Landforms: ten practice questions on terrain and map reading, with concepts and calculations. Every answer is explained.

About 12 minutes.

10 questions.

Ten Middle Ages practice questions test historical concepts and evidence about society, exchange, and change. No calculations. Every answer is explained.

About 12 minutes.

10 questions.

Ancient Civilizations: ten practice questions on institutions and archaeological evidence. Every answer is explained.

About 12 minutes.

10 questions.

Renaissance: ten practice questions on humanism, art, and historical evidence. Every answer is explained.

About 12 minutes.

10 questions.

World War I and Its Aftermath: ten questions on causes, warfare, and the settlement. Concepts, with every answer explained.

About 10 minutes.

10 questions.

19th Century Nationalism and Imperialism: ten questions on state-building and colonial power. Concepts, with every answer explained.

About 11 minutes.

10 questions.

Contemporary History: ten conceptual practice questions on sources, memory, archives, and causation. Every answer is explained.

About 10 minutes.

10 questions.

Key Historical Figures: ten conceptual practice questions on significance, evidence, and reputation. Every answer is explained.

About 10 minutes.

10 questions.

World War II and the Holocaust: ten conceptual practice questions on the war, genocide, and historical evidence. Every answer is explained.

About 12 minutes.

10 questions.

Ten Basic Principles of Marketing questions cover research, value, and delivery, with a conversion-rate calculation. Every answer is explained.

About 12 minutes.

10 questions.

Marketing Mix: ten conceptual practice questions on the four Ps, services, launches, and digital channels. Every answer is explained.

About 11 minutes.

10 questions.

Ten Algebra: Variables and Equations practice questions cover calculations and symbolic reasoning. Every answer is explained.

About 16 minutes.

10 questions.

Change both sides of a linear equation or inequality. Follow the steps, check a value, and see the solution set on a number line.

About 10 minutes.

Ten Logarithms and Their Uses practice questions cover calculations and concepts. Every answer is explained.

About 16 minutes.

10 questions.

Choose a base and a positive value. Compute its logarithm, check the inverse, and compare equal ratios on linear and logarithmic axes.

About 8 minutes.

Ten Ratios and Proportions practice questions cover calculations and concepts. Every answer is explained.

About 16 minutes.

10 questions.

Quadratic Equations: ten practice questions on roots, graphs, and applied calculations. Every answer is explained.

About 14 minutes.

10 questions.

Change quadratic coefficients to compare real roots, the discriminant, the vertex, and the graph.

About 10 minutes.

Exponents and Powers: ten practice questions on power calculations and exponent laws. Every answer is explained.

About 12 minutes.

10 questions.

Basic Arithmetic: ten practice questions on operations, negative numbers, and everyday calculations. Every answer is explained.

About 10 minutes.

10 questions.

Percentages: ten questions on changes, reverse percentages, and percentage points. Includes calculations; every answer is explained.

About 11 minutes.

10 questions.

Probability and Combinatorics: ten questions on counting, conditional probability, and expected-value calculations. Every answer is explained.

About 13 minutes.

10 questions.

Linear Functions: ten questions on slopes, intercepts, and equations. Includes calculations; answers explained.

About 11 minutes.

10 questions.

Explore a linear function by changing slope, intercept, and input. Read its value, zero, and rise over run on a labeled grid.

About 7 minutes.

Roots and Radicals: ten questions on roots and equivalent expressions. Includes calculations; answers explained.

About 11 minutes.

10 questions.

Financial Mathematics: ten practice questions on interest, loans, and present value, with concepts and calculations. Every answer is explained.

About 16 minutes.

10 questions.

Change principal, rate, years, and compounding frequency. Compare compound and simple interest, effective rates, and doubling times.

About 8 minutes.

Fractions and Decimals: ten practice questions with calculations on conversion, arithmetic, ordering, and percentages. Every answer is explained.

About 12 minutes.

10 questions.

Ten Electricity and Magnetism practice questions cover calculations and concepts. Every answer is explained.

About 14 minutes.

10 questions.

Connect two resistors in series or parallel. Compare resistance, current, voltage, and power with an ideal battery.

About 8 minutes.

Ten Energy and Power practice questions combine work, stored energy, power, efficiency, and cost calculations with concepts. Every answer is explained.

About 14 minutes.

10 questions.

Ten Thermodynamics questions combine heat, energy-balance, and efficiency calculations with concepts about equilibrium and entropy. Every answer is explained.

About 14 minutes.

10 questions.

Set two reservoir temperatures and an engine’s efficiency. Compare work and rejected heat with the Carnot limit.

About 8 minutes.

Circular and Rotational Motion: ten questions on turning motion and forces. Includes calculations; answers explained.

About 12 minutes.

10 questions.

Explore uniform circular motion by changing mass, speed, and radius. Compare inward force, acceleration, period, angular speed, and rpm.

About 8 minutes.

Materials and Their Properties: ten questions on density and mechanical response. Includes calculations; answers explained.

About 11 minutes.

10 questions.

Modern Physics: ten practice questions on quantum, nuclear, and relativistic effects, with concepts and calculations. Every answer is explained.

About 15 minutes.

10 questions.

Vary wavelength, work function, and intensity. Compare photon energy, electron energy, stopping potential, and an illustrative photocurrent.

About 8 minutes.

Newtonian Mechanics: ten practice questions on forces and motion, with concepts and calculations. Every answer is explained.

About 12 minutes.

10 questions.

Simulate a cart on a level surface. Change force, mass, and friction, then compare position, velocity, and acceleration graphs.

About 8 minutes.

Complete 32 reasoning items in up to 30 minutes, review your answers, and receive an estimated score. Free, with no sign-up.

About 30 minutes.

32 questions.

Calculate a percentile under a normal distribution with mean 100 and a standard deviation of 15, 16, or 24.

About 2 minutes.