Question

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

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Answer 1

Number is 2115

And value of y is 1

Steps :

21y5 is a multiple of 9

We know that divisibility by 9 rule

If the sum of the digits of a number is divisible by 9, then the number is divisible by 9

So,

2+1+y+5 = 9 or 0

8+y = 9 or 0

8+y = 0 and 8+y = 9

y = - 8 and y = 1

y = - 8 not possible

Hence

y = 1 is the answer