21y7X 9 where why diget what is the value of Y?
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Step-by-step explanation:
Solution:
We know that, according to divisibility rules, if the sum of all the digits of a number is equal to 9 or its multiples, then the number is a multiple of 9.
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.
8 + y = 9
y = 9 - 8
y = 1
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