Last two digits

Find the last two digits of N = 1 1 10 1 N=11^{10}-1 .

1 1 0 0 00 00 000 000 1 -1 2 2

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1 solution

N = 1 1 10 1 = ( 10 + 1 ) 10 1 = 1 0 10 + 10 ( 1 0 9 ) + . . . + 10 ( 10 ) + 1 1 N=11^{10}-1=(10+1)^{10}-1=10^{10}+10(10^9)+...+10(10)+1-1

Each of the terms 1 0 10 + 10 ( 1 0 9 ) + . . . + 10 ( 10 ) 10^{10}+10(10^9)+...+10(10) ends in at least two zeros. Consequently, there is a common factor of 100 100 so that N N ends in 00 00 .

By the way, you should probably make your choices more challenging. 00 is the only option which has 2 digits.

Siva Budaraju - 4 years ago

Also, 11^n if n>=2 the last two digits are 21 so the answer should be 20

Chris Rather not say - 3 years, 11 months ago

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Where did you get that? 11^3=1331.

Siva Budaraju - 3 years, 11 months ago

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I got mixed up

Chris Rather not say - 3 years, 11 months ago

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