SSC CGL Tier II 25 Oct 2015 Paper 1

Question : 23 of 100

Marks: +1, -0

A sum of money placed at compound interest doubles itself in 5 years. It will amount to eight times of itself at the same rate of interest in

Solution:

(4)

{A}= {P} (1+ { {R}}/{100} )^{n}

⇒2 {P}= {P} (1+ { {R}}/{100} )^{5}

On cubing both sides,

2^{3}= (1+ { {R}}/{100} )^{5× 3}

⇒8=1 (1+ { {R}}/{100} )^{15}

∴ Required time = 15 years

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