Page 19 - Start Up Mathematics_5

6. What number comes between the given numbers?

(a) 89,43,500 89,43,502

(b) 3,43,46,999 3,43,47,001

(c) 12,00,00,000 12,00,00,002

Rounding Off Numbers

A newspaper report read, ‘About 4 lakh tickets were sold for the Commonwealth Games’.
Do you think it was the exact number of tickets sold? No, the actual number may have been
3,89,456 but often we round off numbers as an estimate.

We round off numbers to the nearest tens, hundreds, thousands and so on.

Rounding off to the nearest 10

To round off a number to the nearest ten, look at the digit at the ones place.
• If the digit at the ones place is 4 or less, then place a zero at the ones place and let the
digit at the tens place remain as it is.
• If the digit at the ones place is 5 or more, then place a zero at the ones place. Also add
1 to the digit at the tens place.

Example 13: Round off (a) 45,362 and (b) 3,89,427 to the nearest 10.

Solution: (a) 45,362 is rounded off to 45,360 since the digit at the ones place is 2 which
is less than 5.

(b) 3,89,427 is rounded off to 3,89,430 since the digit at the ones place is 7
which is more than 5.

Rounding off to the nearest 100

To round off a number to the nearest hundred, look at
the digit at the tens place. Mental Maths
• If the digit at the tens place is 4 or less, then place zeros Which of these numbers when
at the tens and ones place. The digit at the hundreds rounded off to the nearest
place remains the same. hundred will become 400?

• If the digit at the tens place is 5 or more, then place 349, 378, 415, 464
zeros at the tens and ones place. Add 1 to the digit at
the hundreds place.

Example 14: Round off (a) 2,54,341 and (b) 4,76,586 to the nearest 100.

Solution: (a) 2,54,341 is rounded off to 2,54,300 because the digit at the tens place is 4.
(b) 4,76,586 is rounded off to 4,76,600 because the digit at the tens place is 8.

11