estimateRace – Mental math games online

Seven calculations, four rounded numbers each — round, work it out in your head, tap the closest.

Of the mental math games on MindDuel, estimateRace is the one for estimation. Each calculation shows the rule underneath: round both numbers to one leading digit. Follow it, and your estimate always lands on the right number – none of the four is exact.

Example: Level 2: 46 × 731 – the choices are 20,000, 27,000, 34,000 and 40,000. Solution: 46 ≈ 50 and 731 ≈ 700, so 50 × 700 = 35,000: the closest is 34,000 (exactly 33,626). Round both numbers down – 40 × 700 = 28,000 – and you miss with 27,000.

Levels: All three levels are multiplication: two two-digit numbers on level 1, a two-digit and a three-digit one on level 2, two three-digit ones on level 3; the rule stays the same. Neighboring choices are about 25, 20 and 15 % of the exact result apart, respectively, and you get 7 seconds per round.

estimateRace trains clean rounding under time pressure. Tap 27,000 in the example, and after the round the game names exactly that mistake: “Both numbers rounded down”.