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Digits and Operations

Let us explore the number of digits in the result when we add or subtract the numbers with up
to 6 digits.

Number Smallest Greatest The sum of any Difference between Observation
of digits number number two numbers any two numbers
1 1 9 4 + 5 = 9 5 – 4 = 1 The sum of two 1-digit numbers
1 + 9 = 10 9 – 9 = 0 is a 1-digit or a 2-digit number.
9 + 9 = 18 8 – 1 = 7 The difference of two 1-digit
numbers is always a 1-digit
number.
2 10 99 10 +10 = 20 12 – 12 = 0 The sum of two 2-digit numbers
34 + 57 = 91 85 – 40 = 45 is a 2-digit or a 3-digit number.
10 + 99 = 109 90 – 86 = 4 The difference of two 2-digit
95 + 99 = 194 78 – 10 = 68 numbers is a 1-digit or a 2-digit
number.
3 100 999 100 + 101 = 201 285 – 140 = 145 The sum of two 3-digit numbers
349 + 507 = 856 900 – 899 = 1 is a 3-digit or a 4-digit number.
110 + 999 = 1109 999 – 981 = 18 The difference of two 3-digit
999 + 999 = 1998 852 – 258 = 594 numbers is a 1-digit, 2-digit, or
a 3-digit number.

4 1000 9999
5 10000 99999 94900 – 94899 = 1
99981 – 99900 = 81
28405 – 28040 = 365 The difference of two 5-digit
74123 – 69514 = 4609 numbers is a 1, 2, 3, 4 or a 5-digit
99999 – 11111 = 88888 number.
6 100000 999999 100000 + 100000 The sum of two 6-digit numbers
= 200000 is a 6-digit or a 7-digit number.
349507 + 856110
= 12,05,617

Maths Talk
Try to complete the table for missing operations and observe the number of digits in the result
obtained. Further, add or subtract two numbers having a different number of digits and observe
the number of digits in the result. Discuss with your classmates.

Example 14: Write an example for each of the scenarios below, whenever possible.

(a) 4-digit number + 4-digit number = sum greater than 50,000
(b) 5-digit number + 5-digit number = a 6-digit number
(c) 6-digit number + 3-digit number = a 7-digit number

(d) 5-digit number – 5-digit number = a 3-digit number
(e) 5-digit number – 3-digit number = 4,000

93 Number Play