Trivial
Exam Technique & Timing

Multiple-choice strategy

Elimination, working backwards from the options and spotting common distractors.

5 min read

Before calculating anything, scan the options and eliminate those that are physically impossible. Wrong units, negative values for inherently positive quantities, and magnitudes clearly outside a plausible range can all be spotted in seconds.

Useful elimination checks:

  • Units: if the answer should be in metres and an option is in metres squared: gone.
  • Sign: if you're solving for a distance, length, or probability: eliminate all negatives.
  • Parity (odd/even): the sum of two odd numbers is always even; a product of even numbers is always even. Wrong parity eliminates an option instantly.
  • Magnitude: a 1 s.f. estimate that gives ~2000 eliminates any option of order 200 or 20 000.

Even eliminating just one or two options from a five-option question raises the expected value of a random guess from 20% to 25% or 33%. Under time pressure this matters; every partial insight has value.

Exam tip

Elimination is especially powerful at the end of the paper when time is short. If you're stuck and running low, a ten-second scan to eliminate obviously wrong options is almost always worth it before committing to your best guess.

When the question asks for a specific numerical value, consider substituting each answer option back into the problem rather than solving algebraically from scratch. This avoids messy algebra and turns the question into simple arithmetic verification.

If the options are ordered numerically, start with a middle value. If it's too large, you've eliminated everything equal to or larger; try the next smaller option. In the best case you narrow to one correct answer in two checks.

Worked example

Solve . Options: A) 1, B) 2, C) 3, D) 4, E) 5.

Try B (2): . ✓
Try C (3): . ✓

Both B and C are roots, done without factorising or using the quadratic formula.

Working backwards is also effective for inequalities, "which value satisfies this condition?" questions, and any problem where checking is faster than deriving. Never feel obliged to use the algebraic route if substitution is quicker.

Exam tip

You only need one substitution check per option; as soon as it fails, discard it. Stop the moment you find an option that works (or two, for quadratics with two roots). Don't check remaining options unnecessarily.

Examiners design the wrong options to match the answers produced by predictable errors. Recognising distractor patterns is a form of self-checking; if your answer is one of the options but also exactly matches what a common mistake would produce, treat that as a warning signal.

Common distractor patterns to watch for:

  • Missing a square root or squaring unnecessarily: you solve for but the answer asks for , or vice versa.
  • Sign error: especially with quadratics, completing the square, or negative-exponent index laws.
  • Diameter vs radius: a factor-of-2 error; extremely common in circle area and circumference problems.
  • Partial answer: the penultimate value in a multi-step problem (e.g., the angle when the question asks for the opposite side).
  • Off-by-one: boundary conditions in sequences, combinatorics, and integration limits are reliably tested.

If two options seem equally plausible, look for a factor-of-2 difference or a sign difference between them; those are the most common distractor relationships in the ESAT.

Exam tip

When you arrive at an answer that appears in the option list, ask yourself: what single mistake would each adjacent wrong option represent? If your answer matches what a specific, plausible error gives, double-check that step before selecting.