Study guide · Math Skills Test
The OAR Math Skills Test: Item Types, High-Yield Topics and the Traps
The heaviest-weighted OAR subtest, in depth: what it really asks, how the stems are built, the topics to drill first, and the traps to strike out — then practise it free on this site.
Subtest scope
What the Math Skills Test Really Asks
The Math Skills Test is the largest single share of the OAR — roughly a third of this bank — so it is the first place your study time should go, not the last. It does not ask you to prove theorems or grind long derivations. It asks whether you can move quickly and correctly through arithmetic, algebra, basic geometry and word problems, and whether you can do it in your head and on scratch paper rather than on a calculator. Treat it as a timed reasoning test with four options in front of you, because that framing is what wins it: the answers are part of the problem.
| Content area | What shows up | Roughly how much |
|---|---|---|
| Arithmetic & number sense | Fractions, decimals, ratios, percents, exponents, roots, order of operations | The backbone — expect the most items |
| Algebra | Solve for a variable, linear equations, simple systems, inequalities, expressions | Heavy |
| Basic geometry | Perimeter, area, volume, angles, right triangles, the coordinate plane | Moderate |
| Word problems | Rate · time · distance, work, mixtures, interest, proportions | Woven through the others |
Item taxonomy
Item Types and How the Stems Are Built
Read the answers before you read the stem. On a math item the four options tell you what kind of number you are hunting — a fraction, a percent, a length, a count of hours — and how far apart the traps sit. When the choices are spread wide (2, 20, 200), a rough estimate settles it; when they cluster tight (0.24, 0.42, 0.48), you know the test is checking a decimal place or a sign, and you slow down for exactly that.
The shapes a stem takes
| Item type | What the stem does | Your first elimination move |
|---|---|---|
| Direct compute | “What is 3/8 of 240?” | Estimate the magnitude, cut any option in the wrong ballpark |
| Solve-for-x | Gives an equation, asks for the variable | Back-solve: drop each option in and see which one holds |
| Word problem | A sentence you must translate to math | Name the model (rate, percent, ratio) before touching numbers |
| Geometry | A figure or measurements, asks a length/area | Rule out answers with the wrong units or an impossible size |
| Compare / which-is-greater | Two quantities or expressions | Test a single easy value, then a boundary value |
Priorities
High-Yield Topics to Drill First
Because this is the heaviest subtest, prioritise the topics that appear most and cost the least time to lock down. Fluency with fractions, decimals and percents pays back across arithmetic, algebra and word problems at once — it is the single highest return in the whole OAR. Drill in that order.
Fractions, decimals, percents — convert on sight
Know the common conversions cold (1/8 = 0.125, 1/3 ≈ 0.333, 3/4 = 75%). Half the arithmetic items dissolve the moment you stop reaching for long division.
Percent change and of/is/of translation
“What percent of”, “is what”, and percent increase/decrease recur constantly. Practise turning the sentence straight into part = percent × whole.
Linear equations and one simple system
Isolate a variable in one clean pass, and solve two equations by substitution. Most algebra here stops at that level.
Rate · time · distance and work
d = rt and its cousins power most word problems. Recognise the model first; the arithmetic after is trivial.
Geometry formulas worth memorising
Area and perimeter of rectangles, triangles and circles; volume of a box and cylinder; the Pythagorean theorem. A short, fixed list — learn it once.
Traps & timing
Traps and No-Calculator Time Pressure
The distractors are engineered, not random. The most common trap is the near-duplicate: two options identical except for a decimal place, a sign, or a factor of ten — one is the answer, the other is the mistake the test expects you to make. When you see 0.36 and 3.6 sitting together, that pair is the question. Estimate the size of the answer first and the imposter usually falls out on its own.
There is no calculator to hide behind, so the test is partly measuring mental math under time. That changes strategy: estimate aggressively, round early, and only compute exactly once elimination has left you with two live options. A magnitude check — “this should be a bit under 100” — kills more wrong answers per second than exact calculation ever will.
Estimate the magnitude, strike the impossible, narrow to two, then commit the answer you can defend.
Worked examples
Worked Examples: Eliminate, Then Commit
Three short walk-throughs in the way you should actually work an item — answers first, then eliminate. These are independent practice built to the public subtest outline, not real or retired test items.
Estimate to kill the ballpark
“What is 62% of 148?” with options 9.2, 63, 92, 148. Read the options: 62% of 148 is a bit under two-thirds of 148, so near 90. Strike 9.2 (way low), 63 (too low), 148 (that is 100%). Only 92 survives — commit without exact multiplication.
Back-solve instead of deriving
“If 3x − 7 = 2x + 5, what is x?” with options 2, 5, 8, 12. Rather than rearrange, test the middle: x = 8 gives 24 − 7 = 17 and 16 + 5 = 21 — not equal, and the left side is smaller, so try larger. x = 12 gives 29 = 29. Done, and you never moved a term.
Watch the near-duplicate pair
“A shirt is marked down 20% from $45. What is the sale price?” with options $9, $36, $54, $56.25. The trap $9 is the discount, not the price; $54 and $56.25 are increases, wrong direction. A 20% cut off 45 removes 9, leaving $36 — the only option that is both lower and the right size.
Keep going
Where to Go Next
Subtest · 33
Mechanical Comprehension
The next-heaviest subtest: levers, pulleys, gears, fluids and pressure.
Study desk
OAR study guide
Back to the subtest-by-subtest plan across all three OAR subtests.
Drill it
Free OAR practice test
Work Math Skills items with strike-and-commit, then read every rationale.
FAQ
Frequently Asked Questions
What math is on the OAR?
The Math Skills Test covers arithmetic and number sense (fractions, decimals, percents, ratios, exponents, roots), algebra (solving for a variable, linear equations and simple systems), basic geometry (area, perimeter, volume, angles, right triangles) and word problems that wrap those skills in a sentence. No advanced calculus or trigonometry.
Can you use a calculator on the OAR math section?
Plan and practise as if you cannot — the subtest is built to measure mental math and scratch-paper reasoning under time. The exact aids and materials permitted on test day are set by current NAMI administration guidance and can change, so confirm the rules for your own session rather than relying on a figure you read online.
How hard is the OAR math?
The content stops at solid high-school level; the difficulty is speed without a calculator and distractors designed around common mistakes. Candidates who drill fraction-decimal-percent fluency and practise eliminating options usually find it very manageable. It rewards disciplined reasoning far more than memorised tricks.
OAR Exam Prep
Take the OAR question bank with you
Get the app for the full bank across all three OAR subtests, sampled to the real Math / Mechanical / Reading weighting — or keep drilling free on this site.