Question

If 81x4 is divisible by 3, find the value of x .​

Answer 1

if 81x4 is divisible by 3 then its the sum of its digit are also divisible by 3 ( because of its divisibility rule)

therefore , 8+1+x+4/3 = 13+x/3 .

so let x = 2

therefore 13+2/3 = 15/3 = 5

therefore x = 3

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