We can estimate the answer to an addition sum by rounding the numbers to the nearest hundred before we add.

 

Remember that if a number ends in 50 or above, it rounds up to the next hundred.

If a number ends in 49 or anything below, it rounds down to the previous hundred.

 

Example 1

Estimate the answer to the following sum by rounding the numbers to the nearest hundred and then adding.

 

326 + 567

 

Answer

326 + 567

  ↓        ↓

300 + 600 = 900

 

Example 2

Estimate the answer to the following sum by rounding the numbers to the nearest hundred and then adding.

 

150 + 415

 

Answer

150 + 415

  ↓        ↓

200 + 400 = 600

 

Remember that 150 rounds up to 200, 350 rounds up to 400, 250 rounds up to 300 etc.

 

Are you ready to try some questions now?