Page 20 - Start Up Mathematics_4

By arranging these digits in different positions, many Remember
numbers can be formed.
• To form the greatest number,
68,751; 68,175; 68,157; 67,851; 67,158; 67,518 and so on. arrange the given digits in

The smallest 5-digit number that can be formed using descending order.
these digits is 15,678 and the greatest 5-digit number that • To form the smallest
can be formed is 87,651. number, arrange the given
digits in ascending order.

Example 4: Write the smallest and the greatest 5-digit Quick Tip
numbers formed using the digits 2, 0, 8, 6
and 4. To form the smallest 5-digit
number never place 0 at the
Solution: The smallest 5-digit number formed using ten thousands place, as
the digits 2, 0, 8, 6 and 4 is 20,468 and the it will then become a
greatest 5-digit number formed is 86,420. 4-digit number. So, place
0 at the thousands place.

Example 5: Write the smallest and the greatest 6-digit Mental Maths
numbers formed using the digits 9, 3, 4, 3,
7 and 5. Form the smallest 5-digit
number using the digits 0,
Solution: The smallest 6-digit number formed using 0, 1, 6 and 4.
the digits, 9, 3, 4, 3, 7 and 5 is 3,34,579
and the greatest 6-digit number formed is
9,75,433.

This rack has
Rounding Off Numbers about 100 books.

When we are not sure of the exact number, we use
the word about. It gives a rough estimation of the
number. We can also say that the number has been
rounded off.

Rounding off to the nearest 10

To round off a number to the nearest 10, look at the digit at the ones place.
• If it is 4 or less, then replace it with 0 without changing the digit at the tens place.

• If it is 5 or more, then place a 0 at the ones place and add 1 to the digit at the tens
place.

Example 6: Round off (a) 154, (b) 2,356 and (c) 30,795 to the nearest 10.

Solution: (a) 154 is rounded off to 150 since the digit at the ones place is 4.
(b) 2,356 is rounded off to 2,360 since the digit at the ones place is 6.
(c) 30,795 is rounded off to 30,800 since the digit at the ones place is 5.

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