GMAT® Trick Questions: The Write-It-Down System

If you've ever missed a GMAT® quant question that looked easy — one with a single line of math, no word problem, no setup you could point to — you've felt something that's hard to explain.

You knew the content. You understood the concepts. And you still got it wrong.

Here's what's happening: the simplest problems on the GMAT® are the ones where most people let their guard down. They do the math in their head. They skip writing things out. They rush through eliminations because the problem looks too short to be dangerous.

And the data backs this up. In Episode 28 of Real GMAT® Problems, our podcast series, we walked through three problems from the Official Guide, 11th Edition. The results tell a clear story:

Problem 1 (one line, negative fractions): over a third of test takers miss it
Problem 2 (factor pairs, basic arithmetic): 27% miss it
Problem 3 (multi-step percent translation with algebra): only 17% miss it

The hardest problem to get right was the easiest-looking one. The easiest to get right was the most complex.

That's not a coincidence. It's the pattern this article is about.

The Write-It-Down System

The system has four steps:

When a problem looks simple, write more — not less
Convert mental math into written computation
Write the actual values, not just reasoning about properties
Compare values on a number line or in a list, not in your head

The barrier isn't understanding the system. It's believing you need it.

Most people feel like writing things down on a simple problem is a waste of time. The problem looks too short to justify the scratch work. And for those rare test takers who almost never make careless errors — that instinct might be correct.

For everyone else, the time cost of writing is 3 to 10 seconds. The cost of missing a question you know how to do is much higher.

Problem 1: Negative Fractions and the Cubing Trap

The first problem from Episode 28 is a single line: if $a = -0.3$ , which ordering of $a$ , $a^2$ , and $a^3$ is correct?

Over a third of test takers miss this. 32% choose the same wrong answer — (E) — because they reason about properties in their head instead of computing actual values.

The trap: cubing a negative fraction makes its magnitude smaller (closer to zero), but the value gets larger (less negative). $-0.027$ is bigger than $-0.3$ on the number line. People who do this in their head often reverse that relationship.

The fix: write out $-\frac{3}{10}$ , $\left(-\frac{3}{10}\right)^2$ , and $\left(-\frac{3}{10}\right)^3$ with their actual values, then compare.

Full walkthrough: "If a = -0.3, Which of the Following Is True..." — GMAT® Worked Solution

Problem 2: Factor Pairs and the Negative Sign

The second problem asks: which answer choice is the product of two integers whose sum is 11?

16% of test takers go for (B), which is $-28$ . They find the factor pair $4 \times 7 = 28$ , add $4 + 7 = 11$ , and pick (B). They forget the negative sign. The answer choice is $-28$ , not $28$ . So the factor pairs would be $(-4) \times 7$ or $4 \times (-7)$ , which sum to $3$ or $-3$ — not $11$ .

The correct answer is (A), $-42$ . The factor pair $(-3) \times 14 = -42$ and $(-3) + 14 = 11$ .

Same system: write out each factor pair with the negative sign, compute the sum, compare to 11. Don't do it in your head.

Problem 3: Percent Translation (the One People Get Right)

The third problem is a multi-step percent translation: Mary's income is 60% more than Tim's, Tim's is 40% less than Juan's, what percent of Juan's is Mary's?

This problem has more steps, more math, and more places to make errors. And yet, only 17% miss it — about half the miss rate of Problem 1.

Why? Because the complexity forces people to slow down. They write things out. They set up equations. They use the percent change formula. The problem looks hard enough to justify the work.

That's the irony. The "harder" problems are often safer because they trigger the write-it-down instinct. The simple-looking problems bypass it.

Common Mistakes

Doing property-based reasoning in your head

On the negative fractions problem, people reason: "a squared is positive, a cubed is negative, a fraction cubed gets smaller." All of that's partially correct. But "smaller" in magnitude is not "smaller" in value when the number is negative. Writing the actual computed values catches this.

Forgetting negative signs on factor pairs

On the factor pair problem, people find $4 \times 7 = 28$ and $4 + 7 = 11$ and pick the answer. They forget the answer choice is $-28$ , which means one of the factors must be negative. Writing the negative sign on every factor pair prevents this.

Rushing through simple problems to save time for hard ones

This is the meta-mistake behind both of the above. The instinct to save time on simple problems is understandable — the GMAT® is a timed test, and pacing matters. But missing questions you know how to do is worse than spending 5 extra seconds. The time you save by rushing through a simple problem costs you a correct answer. The time you spend on a hard problem you can't solve may not gain you anything.

Study Action Items

On your next 10 practice problems, time yourself writing things out vs. doing them in your head. Compare the actual time difference — it's probably smaller than it feels.
Pay extra attention to short problems. If a problem is only two or three lines, that's a signal to write more, not less. The GMAT® doesn't put short problems on the test because they're easy. It puts them there because they're easy to get wrong.
For factor pair problems, write the negative sign on every pair when the answer choice is negative. Don't try to track the sign in your head.
For ordering problems (which is bigger, which is smaller), compute the actual values and compare them. Use computed values instead of property-based reasoning — properties have edge cases with negative numbers and fractions.

FAQ

Why do I miss simple GMAT® problems but get hard ones right?

This pattern is common. Simple-looking problems trigger mental math and rushing, which introduces careless errors. Complex problems force you to slow down, write things out, and check your work — which reduces errors. The fix isn't to study more content. It's to apply the same careful process to simple problems that you'd apply to hard ones.

Should I write everything down on the GMAT®?

You don't need to write everything. But on short problems — the ones that look too simple to justify scratch work — that's exactly when to write the most. The time cost is small (usually 3 to 10 seconds). The error reduction is significant. Find your personal balance by timing yourself both ways on practice problems.

How much time does writing things out add?

For most problems, writing out values and computations adds 3 to 10 seconds compared to doing the same work in your head. It can feel longer because mental math feels faster than it is. If you're unsure, time yourself on the same problem both ways and compare.

What should I write down on GMAT® quant problems?

Write what's given, what's asked, and the actual values you're computing. For ordering problems, write each value and compare them. For factor pair problems, write each pair with the sign. For percent problems, write the equations. The goal isn't to write everything — it's to write enough that you don't have to hold intermediate results in your head.

How does this connect to the rate chart system from other episodes?

The rate chart from Episode 44 of our podcast series is the same principle applied to work/rate problems: structure the information on paper instead of holding it in your head. This article covers the broader pattern — the write-it-down instinct applies to every problem type, not just rates.

Want to Learn Even More?

Listen to Episode 28 of Real GMAT® Problems for the full audio walkthrough of all three problems, including Isaac's commentary on why simple problems trick intelligent people and how to build the write-it-down habit.

For related strategy, read:

GMAT® Work/Rate Problems: Why Organization Matters — the rate chart system from Episode 44 of our podcast series
GMAT® Quant: The 'Use What They Give You' Principle — the principle-based approach from Episode 30 of our podcast series

Worked solutions for this episode:

Problem 1: "If a = -0.3, Which of the Following Is True..." — negative fractions and the cubing trap