“It’s about being able to step back and look at your result. Does it make sense?” says Stefan Funk, a particle physicist who ...

You can use estimation to get a rough idea of a calculation. Round the numbers to make it easier. Then do the calculation. If it's really different to the estimation, a mistake has been made.

The number line to 10,000 Learn how to estimate and label numbers up to 10,000 on a number line. Number line to 100 and 1000 Learn how to write and work out numbers on a number line to 1000.