Left-to-right addition, compensation for multiplication and rounding for division — three habits that make mental arithmetic dramatically faster.
Mental arithmetic speed is not a talent, it is a set of specific habits. Most people were taught to calculate on paper from right to left, which is the slowest possible way to do it in your head.
These three habits account for most of the gap between a median and a top-quartile Math Rush score.
Add left to right
Paper addition goes right to left because carries flow that way. In your head, go left to right and keep a running total — you never have to hold the original numbers, only the partial sum.
This halves the memory load, which is the actual bottleneck in mental arithmetic.
Compensate instead of carrying
For 49 × 6, compute 50 × 6 and subtract 6. For 198 + 347, add 200 + 347 and subtract 2. Rounding to a friendly number and correcting is faster and far less error-prone than raw digit-by-digit work.
Compensation is especially strong on the middle level of Math Rush, where the operands are deliberately awkward but near round numbers.
Estimate before you commit
A rough magnitude estimate catches the errors that cost the most: a slipped digit produces an answer that is wrong by a factor of ten, and an estimate catches it instantly.
Spend half a second estimating and you will lose fewer points to typos than you lose to the delay.