Round it fast, round it right.
Mind Sharpness Arithmetic Games Maths Games for Kids (6-10) Maths Games for Juniors (11-14)
Round each number to the place asked for, against the clock. Simple in principle, and the reason it is worth practising is that rounding is the load-bearing skill behind every estimate you will ever make.
The awkward cases are deliberately common here: numbers ending in exactly five, and numbers where rounding up cascades through several digits, like 3,996 to the nearest ten.
This version: Two and three-digit numbers. Your best score is saved in this browser, so you can come back and try to beat it. Nothing is uploaded and no sign-up is needed.
Round half up, the convention taught in most schools worldwide: 45 to the nearest ten is 50.
Because they are where people actually go wrong. Rounding 3,996 to the nearest ten gives 4,000, and the carry through three digits catches out more adults than you would expect.
Directly. Estimating a bill, sanity-checking a total, judging whether an answer is plausible — all of it is rounding first.