Q II (B) Estimate each of the following using general rule:

1. 28,292 - 21,496

Rounding 28292 - 8292 = 20000

20000 + 10000 = 30000

Therefore 28292 is rounded 30000

Similarly 21496 - 1496 = 20000

20000 + 10000 = 30000

Therefore 21496 is rounded to 20000

Thus 30000 - 20000 = 10000 is the answer 

Real difference is 28292 - 21496 = 6796

IN CBSE Board Textbook they have shown rounding of numbers only for tens, hundreds and thousands.

Hence the question should specify upto how many digits you have to round the numbers.

2. 1962+453+ 1538 + 647

Lowest number is 453 so we will round all numbers to hundreds

i) 1962 - 62 = 1900 one end

1900 + 100 = 2000

so 1962 is rounded to 2000

ii) 453 -53 = 400

400 + 100 = 500

therefore 453 is rounded to 500

iii) 1538 - 38 = 1500

1500 + 100 = 1600

so 1538 is rounded to 1500

iv) 647 - 47 = 600

600 + 100 = 700

Therefore 647 is rounded to 600

Hence 2000 + 500 + 1500 + 600 = 4600

This estimate is same as adding 1962 + 453 + 1538 + 647 = 4600

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