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We can estimate the answer to an addition sum by rounding the numbers to the nearest ten before we add.
Remember that a number that ends in five or above rounds up to the next ten.
A number that ends in four or below rounds down to the previous ten.
Example 1
Estimate the answer to the following sum by rounding the numbers to the nearest ten and then adding.
26 + 47
Answer
26 + 47
↓ ↓
30 + 50 = 80
Example 2
Estimate the answer to the following sum by rounding the numbers to the nearest ten and then adding.
94 + 75
Answer
94 + 75
↓ ↓
90 + 80 = 170
Remember that 75 rounds up to 80, 35 rounds up to 40, 25 rounds up to 30 etc.
Let's have a go at some questions now.
