Download NCERT Solutions for Class 8 Maths Chapter 16 Exercise 16.2 – Playing with Numbers
1. If 21y5 is a multiple of 9, where y is a digit, what is the value of y?
Sol.: – For a number to be a multiple of 9, the sum of digit of the number should be divisible by 9.
So, sum of digit of 21y5 = 2 + 1 + y + 5 = (8 + y)
So, to make (8 + y) divisible by 9, we must put y = 1 (since y is a single digit number)
So, y = 1 will make 21y5 a multiple of 9.