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If 21y5 is a Multiple of 9, Where Y is a Digit, What is the Value of Y? - Mathematics

If 21y5 is a multiple of 9, where y is a digit, what is the value of y?

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Solution

If a number is a multiple of 9, then the sum of its digits will be divisible by 9.

Sum of digits of 21y5 = 2 + 1 + y + 5 = 8 + y

Hence, 8 + y should be a multiple of 9.

This is possible when 8 + y is any one of these numbers 0, 9, 18, 27, and so on …

However, since y is a single digit number, this sum can be 9 only. Therefore, y should be 1 only.

  Is there an error in this question or solution?
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APPEARS IN

NCERT Class 8 Maths Textbook
Chapter 16 Playing with Numbers
Exercise 16.2 | Q 1 | Page 260
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