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shekhar

· started a discussion

· 1 Months ago

dimag kharab! (Question: 109778.0 )

99999999999999999999(twenty 9's) is divisible by 11 but not by 27

Question:
(1021-1) is not divisible by:
Options:
A) 3
B) 9
C) 11
D) 27 
Solution:
Ans:(c) We know that (xn - 1) is not divisible by (x+1) for odd values  of n.

\(\therefore\) (1021 - 1) is not divisible by (10+1 = 11) since 21 is on odd number

Vaibhav Yadav

· commented

· 1 Months ago

its simple a^n-b^n is divisible by a+b when n even

Knowledge Expert

· commented

· 1 Months ago

Dear Student,
The given answer is right.
10^21- 1 will contain 21 times 9, not 20 times.
Therefore it will not be divisible by 11.
And also according to solution it is not divisible.

Thanks and Regards
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