SATHEE: Quantitative Aptitude Ques 190

Quantitative Aptitude Ques 190

Question: An amount at compound interest doubles itself in 4 yr. In how many years will the amount become 4 times itself?

Options:

A) 8 yr

B) 12 yr

C) 16 yr

D) 24 yr

Show Answer

Answer:

Correct Answer: A

Solution:

Let Rs. P be the given sum of money. We have $ 2P=P{{( 1+\frac{R}{100} )}^{4}} $

$ \Rightarrow $ $ 2={{( 1+\frac{R}{100} )}^{4}} $

$ \Rightarrow $ $ {2^{\frac{1}{4}}}=( 1+\frac{R}{100} ) $ Let the sum become 4 times in T yr. Then, $ 4P=P{{( 1+\frac{R}{100} )}^{T}} $

$ \Rightarrow $ $ 4={{( 1+\frac{R}{100} )}^{T}} $
$ \Rightarrow $ $ 4={{( {2^{\frac{1}{4}}} )}^{T}} $

$ \Rightarrow $ $ 4={2^{\frac{T}{4}}} $
$ \Rightarrow $ $ 2^{2}={2^{\frac{T}{4}}} $

$ \Rightarrow $ $ T=4\times 2=8yr $

Quantitative Aptitude Ques 189

Quantitative Aptitude Ques 191

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