OAR Exam Flashcards

Q: What is a good OAR score?

OAR scores are reported on a 20-80 scale and the exam is not pass/fail. There is no single national cutoff: minimums differ by Navy program and service. Current MyNavyHR program-authorization examples range from about 42 (Surface Warfare, Supply) to 45 (Civil Engineer Corps) to 50 (Intelligence). Most competitive applicants target the mid-40s or higher.

Q: What subtests are on the OAR?

The OAR has three subtests: the Math Skills Test (arithmetic, algebra, geometry, and word problems), the Reading Comprehension Test (main idea, detail, and inference from short passages), and the Mechanical Comprehension Test (forces and motion, simple machines, gears, fluids, pressure, electricity, and energy). It is the non-aviation portion of the broader ASTB-E.

Q: Can I use a calculator on the OAR?

No. The official ASTB FAQ states calculators are not allowed. You are given scratch paper, and the Math Skills Test is designed to be completed with mental and paper math. Practicing every problem without a calculator is essential so your test-day pacing matches real conditions.

Q: How many times can I take the OAR?

Current Navy Medicine guidance limits candidates to three attempts on the current OAR/ASTB-E series, with at least 30 full calendar days between attempts. Your most recent attempt becomes the official score of record and replaces prior scores, so retaking after a strong result carries real risk. Confirm current timing with your recruiter.

Q: How long does the OAR take and how is it delivered?

The OAR is delivered as a computer-adaptive exam in the APEX system, so question difficulty adjusts to your performance and there is no single fixed item count. The official ASTB FAQ describes the OAR as taking roughly one to two hours total across the three subtests.

Q: How should I study for the OAR Mechanical Comprehension Test?

Focus on the relationships tested most often rather than memorizing trivia: Newton's laws, mechanical advantage of simple machines, gear and pulley ratios, torque and levers, pressure and Pascal's principle, buoyancy, and basic circuits (Ohm's law). Reason through how a change in one variable forces a change in another, since most MCT items test cause and effect.

Question 1

Order of operations (PEMDAS) on the no-calculator MST

Accepted Answer

Resolve in order: Parentheses, Exponents, Multiplication/Division (left to right), Addition/Subtraction (left to right). Multiplication and division share a tier; do whichever appears first reading left to right. A single misordered step is the most common avoidable MST error.

Question 2

Converting between fractions, decimals, and percents quickly

Accepted Answer

Fraction to decimal: divide top by bottom. Decimal to percent: move the point two places right (0.35 = 35%). Percent to fraction: put it over 100 and reduce (25% = 1/4). Memorizing 1/8 = 0.125, 1/3 ≈ 0.333, 3/4 = 0.75 saves time when no calculator is allowed.

Question 3

Rules for operating with signed (negative) numbers

Accepted Answer

Same signs multiplied/divided give a positive; different signs give a negative. Adding numbers with the same sign: add and keep the sign. Different signs: subtract the smaller absolute value from the larger and keep the sign of the larger. Subtracting a negative is the same as adding a positive.

Question 4

Estimation as an MST answer-elimination tool

Accepted Answer

Round each value to an easy benchmark, compute a rough answer, and discard choices that are not close. Because answer choices are usually spread apart, a good estimate often isolates one option without exact computation — a key tactic with no calculator and tight time.

Question 5

Solving a one-variable linear equation

Accepted Answer

Isolate the variable by undoing operations in reverse order: clear parentheses, combine like terms, move variable terms to one side and constants to the other, then divide by the coefficient. Whatever you do to one side you must do to the other.

Question 6

Rule for flipping an inequality sign

Accepted Answer

Solve an inequality like an equation, with one exception: when you multiply or divide both sides by a negative number, reverse the inequality direction (≤ becomes ≥). Forgetting this flip is the classic inequality trap.

Question 7

Laws of exponents

Accepted Answer

Multiplying same base: add exponents (x^a · x^b = x^(a+b)). Dividing: subtract (x^a / x^b = x^(a−b)). Power of a power: multiply (x^a)^b = x^(ab). Anything to the 0 power = 1. Negative exponent means reciprocal: x^(−n) = 1/x^n.

Question 8

The quadratic formula and when to use it

Accepted Answer

For ax² + bx + c = 0, x = [−b ± √(b² − 4ac)] / 2a. Try factoring first; use the formula when factoring is not obvious. The discriminant (b² − 4ac) sign tells you whether there are two, one, or no real solutions.

Question 9

FOIL for multiplying two binomials

Accepted Answer

(a + b)(c + d) = ac + ad + bc + bd — multiply First, Outer, Inner, Last terms, then combine like terms. Recognize the shortcut: (a + b)(a − b) = a² − b² (difference of squares).

Question 10

Setting up a system of two equations from a word problem

Accepted Answer

Assign a variable to each unknown, write one equation per stated relationship, then solve by substitution (isolate one variable and plug in) or elimination (add/subtract equations to cancel a variable). Two unknowns require two independent equations.

Question 11

Sum of interior angles of any triangle and a straight line

Accepted Answer

The three interior angles of any triangle always sum to 180°. Angles on a straight line also sum to 180°, and angles around a point sum to 360°. These let you find a missing angle by subtraction.

Question 12

Pythagorean theorem and common triples

Accepted Answer

For a right triangle, a² + b² = c², where c is the hypotenuse (opposite the right angle). Recognizing the 3-4-5 and 5-12-13 triples (and their multiples like 6-8-10) lets you skip the square root entirely.

Question 13

Area formulas for common shapes

Accepted Answer

Rectangle: length × width. Triangle: ½ × base × height. Circle: πr². Parallelogram: base × height. Trapezoid: ½ × (b₁ + b₂) × height. Height must be perpendicular to the base, not a slanted side.

Question 14

Circle: circumference vs. area, and the diameter trap

Accepted Answer

Circumference = 2πr = πd. Area = πr². The radius is half the diameter — a frequent OAR trap is being given the diameter and using it directly as r. Always check which one the problem provides.

Question 15

Volume of a rectangular box and a cylinder

Accepted Answer

Rectangular solid (box): length × width × height. Cylinder: πr² × height (base area times height). Volume scales with three dimensions, so doubling every side multiplies volume by 8.

Question 16

Similar figures and proportional scaling

Accepted Answer

Similar figures have equal corresponding angles and proportional corresponding sides. If sides scale by factor k, perimeter scales by k, but area scales by k² and volume by k³. Set up a proportion of corresponding sides to find a missing length.

Question 17

Perimeter vs. area — choosing the right one

Accepted Answer

Perimeter is the total distance around a shape (a length, added once around). Area is the space inside (a length squared). Fencing a yard uses perimeter; sodding it uses area. Misreading which is asked is a common word-problem error.

Question 18

Distance-rate-time relationship

Accepted Answer

Distance = Rate × Time. Rearrange as Rate = D/T and Time = D/R. For two objects moving toward each other, add their speeds; moving apart or one catching another, the closing/gap speed is the difference. Keep units consistent (mph with hours).

Question 19

Work-rate (combined work) problems

Accepted Answer

Express each worker's rate as job-per-unit-time (1/time). Add individual rates to get a combined rate, then time = 1 ÷ combined rate. Example: 1/4 + 1/6 = 5/12 of the job per hour, so the job takes 12/5 hours together.

Question 20

Percent change vs. percent of

Accepted Answer

Percent change = (new − old) / old × 100. A successive increase then equal-percent decrease does NOT return to the start (a +20% then −20% leaves you below the original). 'Percent of' multiplies; 'percent change' compares to the original base.

Question 21

Mixture and concentration problems

Accepted Answer

Track the amount of the pure component, not just total volume. (concentration × amount) summed across all parts equals (final concentration × final total). Solving for an unknown volume usually means writing one equation in that variable.

Question 22

Ratio and proportion word problems

Accepted Answer

A ratio a:b can be scaled by a common multiplier x, so the parts are ax and bx and the total is (a+b)x. Set the cross products of a proportion equal (a/b = c/d → ad = bc) to solve for one missing term.

Question 23

Mean, median, and mode — and which resists outliers

Accepted Answer

Mean = sum ÷ count. Median = middle value when ordered (average of the two middle values if the count is even). Mode = most frequent value. The median is far less affected by extreme outliers than the mean.

Question 24

Finding a missing value given a target average

Accepted Answer

Multiply the desired average by the total number of items to get the required total sum, then subtract the sum of the known values. The remainder is the value (or values) you still need.

Question 25

Basic probability of a single event

Accepted Answer

Probability = favorable outcomes ÷ total equally likely outcomes, always between 0 and 1. For independent events both occurring, multiply their probabilities. The probability of an event NOT happening is 1 minus the probability that it does.

Question 26

RCT core rule: answer from the passage only

Accepted Answer

Every correct Reading Comprehension answer must be provable using the text itself, not outside knowledge or assumptions. If you cannot point to the supporting sentence, it is not the answer — even if it is true in real life.

Question 27

Identifying the main idea vs. a supporting detail

Accepted Answer

The main idea is the single point the whole passage supports; a detail is one piece of evidence inside it. A main-idea answer that is too narrow (one detail) or too broad (beyond the passage scope) is wrong. Test it: does every paragraph relate to that statement?

Question 28

Handling inference questions on the RCT

Accepted Answer

An inference must follow logically from stated text with minimal assumption — it is the smallest reasonable step beyond what is written, not a creative leap. Eliminate choices that require information the passage never provides.

Question 29

Vocabulary-in-context strategy

Accepted Answer

Determine the word's meaning from how it is used in the sentence, not its most common dictionary definition. Substitute each answer choice back into the sentence; the right one preserves the author's intended meaning and logic.

Question 30

Eliminating extreme-language distractors

Accepted Answer

Answer choices with absolute words (always, never, all, none, only) are frequently wrong because passages rarely support absolute claims. Moderate, qualified statements (often, may, generally) are more defensible against the text.

Question 31

Author tone and purpose questions

Accepted Answer

Tone is the author's attitude (neutral, critical, persuasive, informative); purpose is why the passage was written (to inform, argue, describe, or analyze). Use word choice and emphasis as evidence, and pick the least extreme tone the text actually supports.

Question 32

Newton's First Law (inertia)

Accepted Answer

An object at rest stays at rest, and an object in motion stays in motion at constant velocity, unless acted on by a net external force. More mass means more inertia and greater resistance to a change in motion.

Question 33

Newton's Second Law

Accepted Answer

Net force = mass × acceleration (F = ma). For a fixed force, more mass means less acceleration. Acceleration is always in the direction of the net force, not necessarily the direction of motion.

Question 34

Newton's Third Law (action-reaction)

Accepted Answer

For every action force there is an equal and opposite reaction force. The two forces act on different objects, so they do not cancel each other — a rocket pushes gas down and the gas pushes the rocket up.

Question 35

Weight vs. mass

Accepted Answer

Mass is the amount of matter and is constant everywhere. Weight is the force of gravity on that mass (W = m × g) and changes with gravitational field — the same object weighs less on the Moon but has the same mass.

Question 36

Friction: static vs. kinetic, and how to reduce it

Accepted Answer

Static friction must be overcome to start motion and is generally larger than kinetic (sliding) friction. Friction opposes motion and increases with the normal force pressing surfaces together. Lubrication, smoother surfaces, or rollers/bearings reduce it.

Question 37

Work in the physics sense

Accepted Answer

Work = Force × distance moved in the direction of the force (W = F × d). If an object does not move, or the force is perpendicular to the motion, zero work is done — holding a weight still does no physics work.

Question 38

Power as the rate of doing work

Accepted Answer

Power = Work ÷ time. Doing the same work faster requires more power. Two engines that lift the same load the same height do equal work, but the faster one is more powerful.

Question 39

Kinetic vs. potential energy and conservation

Accepted Answer

Kinetic energy is energy of motion (depends on mass and speed); gravitational potential energy is stored by height (PE = mgh). In an ideal system energy converts between forms but the total is conserved — a falling object trades PE for KE.

Question 40

Mechanical advantage of a simple machine

Accepted Answer

Mechanical advantage = output (resistance) force ÷ input (effort) force, or equivalently effort distance ÷ resistance distance. A machine multiplies force at the cost of distance (or speed); it does not create energy.

Question 41

The lever law and torque

Accepted Answer

A lever balances when effort × effort arm = resistance × resistance arm. Torque = force × perpendicular distance from the pivot. Moving the effort farther from the fulcrum increases its turning effect, so a longer lever arm needs less force.

Question 42

Three classes of levers

Accepted Answer

First class: fulcrum between effort and load (seesaw). Second class: load between fulcrum and effort, always multiplies force (wheelbarrow). Third class: effort between fulcrum and load, multiplies distance/speed not force (tweezers, forearm).

Question 43

Inclined plane and wedge

Accepted Answer

An inclined plane lets you raise a load with less force over a longer distance; a longer, gentler ramp gives greater mechanical advantage. A wedge is essentially a moving inclined plane that converts a pushing force into splitting/lifting forces.

Question 44

Screw as a simple machine

Accepted Answer

A screw is an inclined plane wrapped around a cylinder. Threads that are closer together (finer pitch) require more turns but less force per turn, giving greater mechanical advantage than a coarse-threaded screw.

Question 45

Pulleys: fixed vs. movable and the strand rule

Accepted Answer

A single fixed pulley only changes the direction of force (MA = 1). A movable pulley multiplies force. In a block-and-tackle, the ideal mechanical advantage equals the number of rope strands directly supporting the load.

Question 46

Gear ratio: speed vs. torque tradeoff

Accepted Answer

A small gear driving a large gear turns the large gear slower but with more torque; a large gear driving a small gear gives more speed and less torque. Two meshed gears always rotate in opposite directions.

Question 47

Belt and chain drives

Accepted Answer

A belt over two pulleys makes both turn the same direction; a crossed belt reverses direction. A smaller driven pulley spins faster than the driver; a larger driven pulley spins slower with more torque. A chain (like gears) does not slip.

Question 48

Pascal's principle and hydraulics

Accepted Answer

Pressure applied to a confined fluid transmits equally in all directions. In a hydraulic system, a small force on a small piston produces a large force on a large piston, scaled by the ratio of piston areas — the basis of mechanical advantage in jacks and brakes.

Question 49

Pressure definition and depth dependence

Accepted Answer

Pressure = Force ÷ Area, so the same force over a smaller area gives greater pressure. In a fluid, pressure increases with depth and does not depend on the container's shape — only on depth, fluid density, and gravity.

Question 50

Buoyancy and Archimedes' principle

Accepted Answer

The upward buoyant force on a submerged or floating object equals the weight of the fluid it displaces. An object floats if it is less dense than the fluid and sinks if it is denser; it floats at the depth where displaced fluid weight equals its own weight.

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