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Using the number line, we can see 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: 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 Think Tank

Using the number line, we can see that 25 is Poonam normally reads 18
exactly midway between 20 and 30. pages of a book every day.
If there are 81 pages in the
In cases where the number lies exactly in the book, estimate the number
middle of the two tens, we round off to the of days in which she will
finish reading the book.
larger tens. So, 25 is rounded up to 30. Answer without calculating.

Math Insight
When rounding off a number to the nearest 10, look at the ones digit.
Š If the ones digit is 4 or less, round down. This means rounding the number to the smaller tens.
Examples: 51, 52, 53 and 54 are rounded down to 50.
Š If the ones digit is 5 or more, round up. This means rounding the number to the larger tens.
Examples: 55, 56, 57, 58 and 59 are rounded up to 60.

Practice time 1F

1. Write the two 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.

romaN Numerals

The symbols that we use today to write numbers are called Hindu-Arabic Numerals.
However, a long time ago, there was another system of representing numbers called the
Roman Numerals. This system started in ancient Rome.

In this system, seven letters of the alphabet are used as basic symbols.

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