Question

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

Answer 1

Answer:

1.

Step-by-step explanation:

Since 21y5 is a multiple of 9, it must accept 9's divisiblity rule.

Testing divisibility rule of 9, which is sum of digits, we get,

Sum of digits in 21y5: 2 + 1 + y + 5

→8 + y

Nearest multiple of 9 to the obtained constant: 9.

So, we get,

8 + y = 9

{Transposing 8 to RHS...}

→y = 9 - 8

→y = 1

Hence, value of y is 1.

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