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example 2: Round off 67 to the nearest 10.
Solution: First of all, identify the two tens between which 67 falls. The two tens are 60
and 70. Draw a number line showing the numbers 60 to 70.
60 61 62 63 64 65 66 67 68 69 70
Looking at the number line, it is clear that 67 is closer to 70 than to 60.
So, 67 is rounded up to 70.
example 3: Round off 25 to the nearest 10.
Solution: First of all, identify the two tens between which 25 falls. The two tens are 20
and 30. Draw a number line showing the numbers 20 to 30.
20 21 22 23 24 25 26 27 28 29 30
Looking at the number line, it is clear that 25 is exactly midway between 20
and 30.
So, 25 is rounded up to 30.
Remember
When rounding off a number to the nearest 10, look at the ones digit.
If the ones digit is 4 or less, round down, that means round the number to the smaller
tens.
Examples: 51, 52, 53 and 54 are round down to 50.
If the ones digit is 5 or more, round up, that means round the number to the larger tens.
Examples: 55, 56, 57, 58, 59 and 60 are round up to 60.
Practice time 1F
1. Write the tens, between which the given numbers lie.
(a) _____ 56 _____. (b) _____ 72 _____. (c) _____ 44 _____.
(d) _____ 89 _____. (e) _____ 106 _____.
2. Round off the following numbers to the nearest tens.
(a) 17 (b) 36 (c) 93 (d) 26 (e) 45
(f) 51 (g) 39 (h) 64 (i) 78 (j) 82
3. Write any 4 numbers that round up to 80.
4. Write any 4 numbers that round down to 100.
24 Mathematics-3
