ASVAB Practice Test Concept Review

Overview

This chapter covers living things, from the tiny cell up to whole ecosystems. You will review the parts of a cell, the main systems of the human body, basic nutrition, how traits pass from parents to children, and how living things depend on one another. Questions are usually short facts, so knowing the key words is the main job.

The cell is the basic unit of life. The nucleus holds the genetic material, DNA, and controls the cell. Mitochondria release energy from food for the cell to use. Plant cells also have a cell wall and chloroplasts, where photosynthesis uses sunlight to make sugar and give off oxygen.

In the body, red blood cells carry oxygen, white blood cells fight infection, and platelets help blood clot. The heart pumps blood, the lungs trade oxygen for carbon dioxide, and the small intestine absorbs most nutrients. Carbohydrates and fats give energy, while proteins build and repair tissue.

For a simple trait, you get two copies of a gene, one from each parent. A dominant trait shows when at least one dominant gene is present, while a recessive trait shows only when both genes are recessive. In an ecosystem, producers such as plants make their own food, consumers eat other living things, and decomposers break down dead material.

Overview

This chapter covers matter and energy: what things are made of and how they move, heat up, and make light and sound. Most questions test a basic rule or a definition, so learn the terms and a few simple formulas.

All matter is made of atoms. An atom has a nucleus with protons, which have a positive charge, and neutrons, which have no charge. Electrons, with a negative charge, move around the nucleus. Matter is usually found as a solid, a liquid, or a gas, and adding or removing heat changes it from one state to another.

A force is a push or a pull. Newton's laws say that an object keeps doing what it is doing unless a force acts on it, that force equals mass times acceleration, and that every action has an equal and opposite reaction. Energy can change form, for example from stored energy to motion, but it is not created or destroyed.

Heat moves in three ways: conduction through direct touch, convection through moving liquids or gases, and radiation through waves, such as heat from the sun. Sound is a wave that needs a medium such as air or water, so it cannot travel through a vacuum. Light can travel through empty space and moves much faster than sound.

Overview

This chapter covers the Earth itself, the air around it, and its place in the solar system. You will review the three main kinds of rock, the layers of the atmosphere and basic weather, and the movements of the Earth and Moon.

Rocks are grouped by how they form. Igneous rock forms when melted rock, called magma or lava, cools and hardens. Sedimentary rock forms when layers of sand, mud, or shells pile up and press together. Metamorphic rock forms when heat and pressure change an existing rock.

The atmosphere is the layer of gases around the Earth, and it is mostly nitrogen with a smaller share of oxygen. Weather happens in the lowest layer, the troposphere. The ozone layer, higher up in the stratosphere, blocks much of the sun's ultraviolet light.

The Earth spins on its axis once a day, which gives us day and night. It travels around the sun once a year. Seasons happen because the Earth's axis is tilted, not because the Earth gets closer to or farther from the sun. The Moon's pull is the main cause of ocean tides.

Overview

This chapter is about turning a short story into a math problem and solving it. The math itself is usually simple, such as adding, multiplying, or finding a percent. The hard part is reading carefully, picking out the numbers you need, and choosing the right formula.

Many problems use a few standard formulas. Distance equals rate times time. An average is the total divided by the number of items. Simple interest equals principal times rate times time. A percent means a number out of 100, so 25 percent is 0.25.

Ratio and proportion problems compare two amounts. If 3 cans cost 6 dollars, you can set up 3 over 6 equals 5 over x and cross-multiply to find the cost of 5 cans. For percent change, divide the amount of change by the original amount, not by the new amount.

A good habit is to write down what the question asks before you start. Watch the units, such as minutes versus hours or inches versus feet, and change them so they match. After you get an answer, check that it makes sense in the story.

Overview

This chapter is about word meanings. Each question gives a word, either by itself or inside a sentence, and asks which choice means most nearly the same thing. A wide vocabulary helps most, but a few skills can help you handle words you are not sure about.

When the word is in a sentence, read the whole sentence first. The other words often give a clue, such as a contrast word like but or although, or an example that explains the meaning. Try putting each answer choice in place of the word and see which one keeps the sentence's meaning.

Word parts are another strong tool. A root carries the main meaning, a prefix at the front changes it, and a suffix at the end often shows whether the word is a noun, verb, or adjective. For example, the prefix un- means not, and the root port means carry.

Some words also have a positive or negative feeling. If you can tell whether a word sounds good or bad, you can often rule out choices with the opposite feeling. Read all the choices before you pick, because two may look close and only one is the best match.

Overview

This chapter is about reading a short passage and answering a question about it. The passages are only a few sentences or a short paragraph long. The questions usually ask for the main idea, a stated detail, the meaning of a word in context, or a conclusion you can draw.

The main idea is what the whole passage is about. It is often in the first or last sentence, but not always. A wrong choice may be a true detail from the passage that is too narrow, or a broad idea that the passage never actually covers.

Detail questions ask about something the passage says directly, so go back and find the exact words. Inference questions ask what the passage suggests without saying it outright. The right answer must follow from the passage, not from your own outside knowledge or opinions.

When a question asks about a word in context, reread the sentence and the ones around it. The word may have a different meaning from the one you know best. Read the question first, then the passage, so you know what to look for.

Overview

This chapter covers the rules of numbers and basic algebra. You will review signed numbers, the order of operations, exponents and square roots, solving equations and inequalities, and factoring. Many questions can be solved quickly if you know the rules well.

When you multiply or divide two numbers with the same sign, the answer is positive. When the signs are different, the answer is negative. The order of operations is parentheses first, then exponents, then multiplication and division from left to right, then addition and subtraction from left to right.

An exponent tells how many times to multiply a number by itself, so 3 squared is 3 x 3 = 9. When you multiply powers with the same base, add the exponents. A square root is the number that, times itself, gives the original number, so the square root of 49 is 7.

To solve an equation, do the same thing to both sides until the variable is alone. Inequalities work the same way, except that multiplying or dividing both sides by a negative number flips the inequality sign. Factoring breaks an expression into parts that multiply together, such as x squared - 9 = (x + 3)(x - 3).

Overview

This chapter covers shapes and space. You will review angles, triangles, the perimeter and area of flat shapes, circles, and the volume of solid shapes. Most questions ask you to pick the right formula and do a short calculation.

Angles are measured in degrees. A right angle is 90 degrees, a straight line is 180 degrees, and two angles that add to 90 degrees are complementary while two that add to 180 degrees are supplementary. The three angles inside any triangle add up to 180 degrees.

In a right triangle, the Pythagorean theorem says a squared plus b squared equals c squared, where c is the longest side, the hypotenuse. Perimeter is the distance around a shape, and area is the space inside it. A rectangle's area is length times width, and a triangle's area is one-half times base times height.

For a circle, the radius goes from the center to the edge and the diameter is twice the radius. The circumference is pi times the diameter, and the area is pi times the radius squared. The volume of a box is length times width times height, and the volume of a cylinder is pi times the radius squared times the height.

Overview

This chapter covers how electricity works and how circuits are built. You will review current, voltage, and resistance, Ohm's law and power, series and parallel circuits, and common parts such as resistors, fuses, and switches.

Current is the flow of electric charge and is measured in amperes. Voltage is the push that moves the current and is measured in volts. Resistance slows the current and is measured in ohms. Ohm's law ties them together: voltage equals current times resistance. Power, measured in watts, equals voltage times current.

In a series circuit, parts are connected in one path, so the same current flows through each part and the resistances add up. If one part breaks, the whole circuit stops. In a parallel circuit, each part has its own branch, so each branch gets the full voltage and the others keep working if one fails.

Conductors, such as copper, let current flow easily, while insulators, such as rubber and plastic, block it. A fuse or circuit breaker opens the circuit when too much current flows, which protects the wiring. Direct current flows one way, like from a battery, and alternating current changes direction, like household power.

Overview

This chapter covers how cars and trucks work. You will review the engine and its four-stroke cycle, the fuel, ignition, and cooling systems, and the brakes, steering, suspension, and electrical parts. Questions often ask what a part does or what causes a common problem.

Most gasoline engines use a four-stroke cycle. On the intake stroke, the piston moves down and pulls in air and fuel. On the compression stroke, the piston moves up and squeezes the mixture. A spark plug then fires for the power stroke, which pushes the piston down, and the exhaust stroke pushes the burned gases out.

The cooling system keeps the engine from overheating. A water pump moves coolant through the engine, the radiator gives off the heat to the air, and the thermostat controls when coolant flows to the radiator. The lubrication system uses oil to reduce friction between moving parts.

Most cars use hydraulic brakes, where pressing the pedal pushes brake fluid from the master cylinder to each wheel. Disc brakes use pads that squeeze a rotor, and drum brakes use shoes that press against a drum. The battery starts the car, and the alternator recharges the battery and powers the electrical system while the engine runs.

Overview

This chapter covers common shop tools and how they are used. You will review hand tools, power tools, measuring and layout tools, fasteners, and basic materials. Many questions show or describe a tool and ask what it is used for.

Hand tools include hammers, screwdrivers, wrenches, pliers, saws, and files. Each one has a job: a claw hammer drives and pulls nails, a box-end wrench grips all six sides of a nut, and a file smooths or shapes metal. A torque wrench tightens a bolt to a set tightness, and a miter box guides a saw for angle cuts.

Measuring and layout tools help you work accurately. A tape measure or rule measures length, a level checks whether a surface is level (horizontal) or plumb (straight up and down), and a square checks right angles. A micrometer and a caliper measure small sizes very precisely.

Fasteners hold parts together. Nails and wood screws are for wood, bolts go through parts and are held with nuts, and rivets join parts permanently. A washer spreads the load under a bolt head or nut, and a lock washer helps keep a nut from loosening.

Overview

This chapter covers how simple machines and basic forces work. You will review levers, pulleys, gears, inclined planes, and pressure in liquids and gases. Most questions ask which way something moves or how much force is needed.

A simple machine makes work easier by trading force for distance. With a lever, a longer effort arm means less effort is needed: effort times effort arm equals load times load arm. A pulley system with more rope sections holding the load needs less pulling force, but you must pull more rope.

Gears pass motion from one shaft to another. Two meshed gears turn in opposite directions. A small gear driving a large gear makes the large gear turn slower but with more turning force, and a large gear driving a small one makes the small gear turn faster.

An inclined plane, or ramp, lets you raise a load with less force by moving it a longer distance. A screw is an inclined plane wrapped around a post. Pressure is force divided by area, and in a hydraulic system a small force on a small piston can make a large force on a large piston.