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Example 7: Subtract 546 from 978 using the expanded form.

Solution: Step 1: Expanded form

9 7 8 = 900 + 70 + 8
5 4 6 = 500 + 40 + 6

Step 2: H T O Hundreds Tens Ones

9 7 8 9 0 0 7 0 8
– 5 4 6 – 5 0 0 – 4 0 – 6

4 0 0 3 0 2

Step 3: H T O

4 0 0

3 0
+ 2

4 3 2 So, 978 – 546 = 432.

Estimating the Difference

To estimate the difference, round off the given minuend and subtrahend to the nearest
10, 100, 1000, etc., and then subtract.
Example 8: Subtract 448 from 626 using estimation method by rounding off each number
to the nearest 100.

Solution: H T O H T O

6 2 6 6 0 0 (626 is rounded off to 600)
– 4 4 8 – 4 0 0 (448 is rounded off to 400)

2 0 0

Example 9: Find the difference between 692 and 454 using estimation method to the

nearest 10 and compare with the actual value.
Solution: Actual value Estimated value

H T O H T O
8
12
6 9 2 6 9 0 (692 is rounded off to 690)
– 4 5 4 – 4 5 0 (454 is rounded off to 450)

2 3 8 2 4 0

The actual value 238 when rounded off to the nearest 10 is 240.
So, the estimated value 240 is very close to the actual value 238.

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