# Use estimation and rounding to check the reasonableness of answers to calculations (ACMNA099)

LO: To round numbers to check the reasonableness of answers
Know:

• how to round numbers for estimation
• the place value of whole numbers

Understand:

• that rounding numbers to a specified number to check answers makes life easier
• rounding numbers can give us a quick estimation of the reasonableness of answers

Do:

• I can round numbers to check the reasonableness of answers

Rounding Numbers

Rounding numbers is fairly easy. There is just 1 simple rule, if the next number in line is equal or greater than >= 5 then you round the number up. If the next number in line is less than < 5, then you round the number down.   When rounding always check to the number to the right of the number in which you want to round it to.

For example, if you want to round the number to the nearest tens, then look at the units to see if it is greater than or less than 5.

If you want to round the number to the nearest hundred, then look at the tens to see if it’s greater than or less than 5.