SSC Sample Paper Mock Test-11 SSC CGL Tear-II Paper-1

With a given rate of simple interest, the ratio of principal and amount for a certain period of times is 4 : 5. After 3 yr, with the same rate of interest, the ratio of the principal and amount becomes 5 :7 rate of interest is

A)                      4%

B) 6%

C) 5%

D) 7%

Correct Answer: C

Solution :

Case I

Interest \[=5x-4x\]= Rs. \[x\]

\[\therefore \] \[x=\frac{4x\times R\times T}{100}\]\[\Rightarrow \]\[T=\frac{25}{R}\text{yr}\]

Case II \[T=\frac{25}{R}+3=\left( \frac{25+3R}{R} \right)\,\,\text{yr}\]

\[SI=7y-5y\]= Rs. 2y

\[\therefore \] \[2y=\frac{5y\times R\times (25+3R)}{R\times 100}\]

\[\Rightarrow \] \[40=25+3R\]\[\Rightarrow \]\[3R=40-25=15%\]

\[\therefore \] \[R=\frac{15}{3}=5%\]