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Sam ji

· started a discussion

· 1 Months ago

Two options not satisfying. Pls explain. (Question: 109778.0 )

Pls explain how it is divisible by 27.. though it is not divisible by 11 either . But the above expression is also not divisible by 27.
Since 27 divides 999 completely ,i.e., 27 divides when 999...n is in multiple of 3 whereas in above Q: 99999...20 times.
Pls confirm.
Thanx.

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

Knowledge Expert

· commented

· 1 Months ago

Dear Student,
10^21 - 1 will contain 21 times 9 , not 20 times.
So it will be divisible by 27.

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