A number theory problem by Gajender Singh
Number Theory
Level
pending
IF 2 raise to the power 36 -1=68a19476735. Find the value of a.
The answer is 7.
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1 solution
2 raise the power -1 is divisible by 9. Then 68a............ should also be divisible by 9. And the divisibility rule for 9 is that the sum of the digits should be divisible by 9. Hence 6+8+a+.... is divisible by 9. Sum comes to be 56+a. the next no. after 56 divisible by 9 is 63. Then a value should be single digit 7 .( As 56+7=63)