Page 23 - Maths Skill - 3

4-digit Numbers 21

Example 3: Form the greatest 4-digit number using the digits 5, 4, 2, 7.

Solution: Arranging the digits in descending order, we get:
7 > 5 > 4 > 2

Thus, the greatest 4-digit number using the digits is 7542.

Successor and Predecessor

The number that comes just after a particular number is called its successor. Thus, a
successor of a number is always 1 more than the number.

For example, successor of 1356 = 1356 + 1 = 1357 Fact-o-meter

The number that comes just before a particular � We add 1 to the number to get
its successor.
number is called its predecessor. Thus, a � We subtract 1 from the number
predecessor of a number is always 1 less than the to get its predecessor.
number. � A number has one successor
For example, predecessor of 1234 = 1234 – 1 = 1233 and one predecessor.

Skip Counting

When we count or write numbers after skipping a fixed gap between two successive
numbers, it is called skip counting.
For example:

Skip Counting in 2s Skip Counting in 10s

+2 +2 +2 +2 +2 +10 +10 +10 +10 +10

1123 1125 1127 1129 1131 1133 2445 2455 2465 2475 2485 2495

Skip Counting in 100s Skip Counting in 1000s

+100 +100 +100 +100 +100 +1000 +1000 +1000 +1000 +1000

5632 5732 5832 5932 6032 6132 1636 2636 3636 4636 5636 6636

Exercise 2.7

1. Form the greatest and the smallest 4-digit numbers that can be made using the
following digits.

Digits Greatest Number Smallest Number

(a) 3, 4, 8, 7

(b) 7, 3, 0, 0