Find the rate of interest if the amount after 2 years of simple interest on a capital of Rs. 1200 is Rs. 1440.

18%
29%
310%
411%

Answer:- 1

Explanation:-

Solution:

\begin{aligned} Amount, A = R s . 1440 \\ Principal, P = R s . 1200 \\ Interest, I = R s . (1440 - 1200) = 240 \\ R = \frac{(240 \times 100)}{(1200 \times 2)} = 10 % \\ Alternatively, \\ We can go through a thought process i . e . \\ 1200 - - 20 % ↑ (240 in 2 years) - - > 1400 \\ That means 10 % rise in each year \end{aligned}

$\eqalign{ & {\text{Amount}},\,A = Rs.\,1440 \cr & {\text{Principal}},\,P = Rs.\,1200 \cr & {\text{Interest}},\,I = Rs.\,\left( {1440 - 1200} \right) = 240 \cr & R = \frac{{\left( {240 \times 100} \right)}}{{\left( {1200 \times 2} \right)}} = 10\% \cr & \cr & {\text{Alternatively}}, \cr & {\text{We}}\,{\text{can}}\,{\text{go}}\,{\text{through}}\,{\text{a}}\,{\text{thought}}\,{\text{process}}\,i.e. \cr & 1200\, - - 20\% \uparrow \left( {240\,{\text{in}}\,2\,{\text{years}}} \right) - - > 1400 \cr & {\text{That}}\,{\text{means}}\,10\% \,{\text{rise}}\,{\text{in}}\,{\text{each}}\,{\text{year}} \cr}$