RRB Group-D Model Paper 20 with answers for online practice

Question : 40 of 100

Marks: +1, -0

2^16

– 1 is divisible by

Solution:

Formula:

a^2 – b^2

= (a + b) (a – b)

2^16

– 1
=

(2^8)^2

– 1
=

(2^8 + 1) (2^8 – 1)

= 257 × 255
= 257 × 15 × 17
Thus it is divisible by 17 as 17 is a factor.

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