Sequence And Series Question 420

Question: Let a = 111… 1(55 digits), $ b=1+10+10^{2}+…+10^{4}, $ $ c=1+10^{5}+10^{10}+10^{15}+….+10^{50}, $ then

Options:

A) $ a=b+c $

B) $ a=bc $

C) $ b=ac $

D) $ c=ab $

Show Answer

Answer:

Correct Answer: B

Solution:

[b] $ a=1+10+10^{2}+….+10^{54} $ $ =\frac{10^{55}-1}{10-1}=\frac{10^{55}-1}{10^{5}-1}.\frac{10^{5}-1}{10-1}=bc $