Timed Mental-Math Drill
Dozens of quick sums, one ticking clock, no calculator — the kind of fast arithmetic markets interviews commonly include.
Why there's a clock
A lot of markets roles involve doing quick sums in your head while other things are happening — so interviews often check that you can. A classic format is a page of arithmetic (or an on-screen version) with a tight time limit: lots of questions, only a few minutes, no calculator.
The good news is that it's one of the parts you can most easily practise for. Nobody is born fast at this; people get fast by doing reps. So let's do some.
How to read your result
Your headline number is simply how many you got right. The panel also shows your pace — correct answers per minute — which is the fairest way to compare a 60-second sprint with a 2-minute run. Accuracy keeps you honest: fast but sloppy is worse than steady and right.
Don't chase any particular figure. The only comparison that matters is you versus your last few rounds — watch the pace drift upward as the sums start to feel familiar.
You just did that the honest way — sum by sum. The fast people lean on a handful of tricks: round-and-adjust, breaking numbers into easy parts, and instant fraction↔percent swaps that do half the work for you. That toolkit is the next lesson, Fractions, % & Fast Estimation — and the pace you just scored is your before-and-after baseline. Here's a taste:
- 48 is awkward, but 50 is easy. Round up: 7 × 50 = 350.
- You added 2 to each of the seven, i.e. 7 × 2 = 14 too much. Take it back off.
- 350 − 14 = 336. That 'round, then adjust' move is the heart of fast mental math.
Check your understanding
- Many markets interviews include a timed, no-calculator arithmetic section.
- It rewards calm, practised speed and accuracy — not raw talent.
- 'Round then adjust' (7 × 48 = 7 × 50 − 14) is the core shortcut; more in the next lesson.
- Track your own pace and accuracy over rounds — the only benchmark that matters is your last round.