Solve as many math problems as you can in 30 seconds.
An arithmetic problem (+, −, ×) appears with 4 answer choices.
Tap the correct answer to advance. Wrong taps cost 2 seconds.
Goal: solve as many as possible in 30 seconds.
Speed here comes from skipping full calculation, not from doing arithmetic faster. For multiple-choice answers you can often eliminate options by their last digit or their size alone — if the sum must end in 7, the only choice ending in 7 is correct without finishing the maths. Estimation knocks out the obviously-too-big or too-small answers in a glance.
Because a wrong tap costs two seconds, never gamble on a problem you have not actually read; that penalty erases several correct answers. Keep your thumb near the centre of the four choices so any of them is a short move away, and settle into a metronome rhythm. A steady stream of certain answers always outscores a fast burst broken up by mistakes.