RRB NTPC 2014 Paper

Question : 25 of 100

Marks: +1, -0

An amount of ₹ 15000 was invested for 3 years at annual compound interest. If the amount received was ₹ 19965, then what was the rate of interest?

Solution:

(3) Let the rate of compoundinterest be r% per annum. Now,

{19965}/{15000}= (1+ {r}/{100} )^{3}

\⇒ {15 × 1331}/{15 × 1000}=\ ( {11}/{10}\ )^{3}

=\ (1+\ {r}/{100}\ )^{3}

\⇒ \ {11}/{10}=1+\ {r}/{100}

\⇒ \ {r}/{100}=\ {11}/{10}-1=\ {1}/{10}

Therefore,

r=10 \%

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