GMAT® Execution Habits: The Scratch-Work System for Easy Questions

An easy question can feel like a free point, and skimming through it makes sense: the math underneath is grade-school familiar, and the clock is running. The scoring algorithm on the GMAT® complicates that instinct, because it takes a question's difficulty into account when it computes your score. A miss on something easy typically costs more than a miss on something hard, which turns the questions you know cold into the ones your habits have to protect.

Episode 12 of our Real GMAT® Problems series works through three Official Guide problems from the 11th edition, and all three run the same experiment: middle school math on top, an execution test underneath. One problem is a two-line substitution with three ways to go wrong. One is a fraction whose numerator is a sum, built to see whether canceling gets applied where it isn't legal. One is a system of equations where the only dangerous step is the last one. None of the habits takes more than a few seconds to write down, and they live in the scratch work.

Habit 1: Parentheses Around Everything You Plug In

When a problem states that $x = -3$, substitution is the whole job, and the habit that keeps the job clean is writing parentheses around whatever goes in. The expression $-3x^2$ becomes $-3(-3)^2$, and those parentheses carry information: the base of the exponent is negative three, all of it.

Without them, the same substitution reads $-3 \times -3^2$, and by the standard convention $-3^2$ means $-(3^2)$, or $-9$. Multiply that by $-3$ and the result is $27$, a wrong answer parked among the choices. There's a second wrong turn too: multiplying before squaring produces $81$. One habit, adopted in two seconds, prevents both.

The full walkthrough, including where each wrong answer comes from, is in "If x = -3, What Is the Value of -3x²?" — GMAT® Worked Solution.

Habit 2: Split or Factor Before You Cancel

A fraction with a sum on top invites a shortcut that feels like math: canceling the denominator against one term of the sum and moving on. Canceling is division, and division reaches every term, so the moves that work are the ones that reorganize the sum first.

On $\frac{29^2 + 29}{29}$, one route splits the fraction back into $\frac{29^2}{29} + \frac{29}{29}$, which is $29 + 1$. The other factors the numerator into $29(29 + 1)$, which turns the sum into a product the 29 can cancel through cleanly. Both arrive at 30. The one-term cancellation arrives at 58, and about 4% of test takers pick it.

"What Is the Value of (29² + 29)/29?" — GMAT® Worked Solution runs both approaches side by side.

Habit 3: Write Every Operation Under Both Sides

Solving $1 - 3t = 2t - 1$ for $t$ takes three short moves, and none of them is the risky part. The risky part is the last line, where a value that survived the whole solve comes out flipped: $2 = 5t$ turns into $t = \frac{5}{2}$ instead of $t = \frac{2}{5}$, and about 3% of test takers submit the inverted version.

The habit that protects the last line is writing each operation under both sides of the equation while solving, so $\div 5$ appears on the page under the left side and the right side before the final answer gets read off. A recorded step can be checked; a mental leap leaves nothing to check.

"If x = 1 - 3t and y = 2t - 1, for What Value of t Does x = y?" — GMAT® Worked Solution has the full solution, scratch-work layout included.

Common Mistakes

Skipping the parentheses on substitutions that look safe. The habit matters most when the plugged-in value is negative or compound, and it only becomes automatic if it gets used everywhere, easy problems included.

Canceling one term of a sum. $\frac{29^2 + 29}{29}$ isn't $29 + 29$. A denominator divides everything above it, and the legal routes (splitting the fraction, or factoring the numerator first) are the moves that respect that.

Inverting the fraction on a clean solve. $2 = 5t$ means $t = \frac{2}{5}$. The error survives because every step before it was right, which is exactly why the final division deserves its own written line.

Doing easy problems entirely in your head. Mental math feels efficient on questions this short, and it removes the page record that catching a mistake depends on.

Study Action Items

• Start the parentheses habit on the very next practice problem, easy or hard, because a habit that only runs on hard problems probably won't be there on test day.
• When a fraction has a sum on top, decide between splitting and factoring before anything gets canceled.
• Write each operation under both sides of the equation in scratch work, even when the algebra is two moves long.
• During review, check the wrong answers on easy questions and note which habit would have caught each one.

Problems From This Episode

• "If x = -3, What Is the Value of -3x²?" — GMAT® Worked Solution
• "What Is the Value of (29² + 29)/29?" — GMAT® Worked Solution
• "If x = 1 - 3t and y = 2t - 1, for What Value of t Does x = y?" — GMAT® Worked Solution

FAQ

How do I stop making careless mistakes on easy GMAT® quant questions?

Replace attention-dependent execution with physical habits: parentheses around every substitution, reorganizing before canceling, and writing each operation under both sides. Attention can waver under time pressure, so the fix is a record on the page that can be checked, not more focus.

Why do mistakes on easy GMAT® questions cost more than mistakes on hard ones?

The scoring algorithm takes each question's difficulty into account, so a miss on a question that over 90% of test takers answer correctly moves your score more than a miss on a hard one does. An easy miss is also a signal worth reading: it usually points at an execution gap rather than a knowledge gap, and execution gaps respond quickly to habit changes.

Can you cancel a denominator with only one term on top of a fraction?

No. Canceling is division, and division reaches every term of the numerator. On $\frac{29^2 + 29}{29}$, the denominator has to divide both $29^2$ and $29$, which is what splitting the fraction does: $\frac{29^2}{29} + \frac{29}{29} = 29 + 1$. Factoring works too, because $29(29 + 1)$ turns the sum into a product that the 29 can cancel through.

What does $-3x^2$ mean when $x = -3$?

It means $-3(-3)^2$: the exponent applies to the parenthesized value first, so $(-3)^2 = 9$, and then the leading $-3$ multiplies, giving $-27$. Without the parentheses, the convention $-3^2 = -(3^2) = -9$ takes over and the expression evaluates to $27$. The parentheses decide the answer.

How do I avoid flipping a fraction at the end of an algebra problem?

Write the final operation under both sides of the equation before computing it. If $2 = 5t$, write $\div 5$ under each side, then read off $t = \frac{2}{5}$. The inversion error lives in the gap between solving and writing the answer, and a recorded step closes that gap.

Want to Learn Even More?

Listen to Episode 12 of Real GMAT® Problems from The GMAT® Strategy Podcast for the full discussion, including the case for revisiting basic material, and the honest origin of the write-it-down habit: missing questions like these until the habit stuck.

Related reading:

• How Writing Down More Improves Your GMAT® Score
• Be Accurate to Improve Your GMAT® Score: Why Precision Comes Before Speed
• GMAT® Exponents and Roots: A Complete Guide