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eSTImATING SUmS AND DIFFeReNCe

Estimation is the process of getting an approximate amount, sum or difference.

examples: 1. Estimate 34. We found the range of 30-40 for the number line. The

middle number is 35. The place for 34 is closer to 30. That means 34

is estimated to be 30.

30 31 32 33 34 35 36 37 38 39 40

2. Estimate 37. Here also, the place for 37 is closer to 40. That means

37 is estimated to be 40.

30 31 32 33 34 35 36 37 38 39 40

estimating Sums

To estimate the sum, we round off each number to the nearest tens and then add

the rounded-off numbers.

example 1: There are 86 coconut and 42 chocolate cookies in a jar. Estimate the

total number of cookies.

Solution: Round the numbers to the nearest ten and add.

For two-digit numbers, we can round the number to the nearest tens

place. That is only one place estimate.

Actual sum estimated sum
8 6 Rounded up 9 0

+ 4 2 Rounded down + 4 0

1 2 8 1 3 0

There are approximately 130 cookies.

The actual number of cookies is 128.

The estimated sum differs from the actual sum by 2.

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