The fastest way to get quicker at mental math is to stop calculating and start recognising. People who are fast at sums in their head are rarely doing more arithmetic than you. They have just seen the same patterns so often that the answer comes back the way a familiar word does when you read it. You build that with a handful of tricks and steady practice.
Learn your times tables until they are automatic
Multiplication is the foundation, and the times tables up to 12 are the part worth knowing cold. When 7 times 8 comes back instantly instead of being worked out, every larger multiplication and every division gets faster too, because they all lean on those facts. If any square in the table still makes you pause, that is the first place to drill.
Round to a friendly number, then adjust
Big additions and subtractions get much easier when you bend them toward round numbers. To add 47 and 28, add 47 and 30 to get 77, then take the extra 2 back for 75. To subtract 19, take away 20 and add 1 back. You trade one awkward step for two easy ones, and easy steps are where accuracy lives.
Break numbers apart
Splitting a number into its tens and units lets you work the easy parts first. To multiply 23 by 4, do 20 times 4 for 80 and 3 times 4 for 12, then add them for 92. The same idea works for addition: handle the tens, handle the units, then combine. It keeps the running total small enough to hold in your head.
Practise little and often
A few minutes a day beats one long session a week. The goal is not endurance but repetition, so the common sums settle into memory. The mental math test is built for exactly this: one minute, as many problems as you can, with a difficulty you can step up as the easier sums start to feel automatic.
Match difficulty to where you are
Start on the level you can clear cleanly, not the one that looks impressive. Accuracy comes first, because a fast wrong answer is worth nothing. Once you are scoring well with few mistakes, move up a level. The jump will feel hard at first, which is the point, and your numbers will climb again as the new patterns sink in.
Try it yourself
Run the mental math test on easy to find your baseline, use the tricks above for a week, then run it again. You will usually see the score move, partly from sharper arithmetic and partly from getting used to the rhythm of answering quickly. For a different kind of number challenge, the number memory test measures how many digits you can hold at once.