## Aptitude question and answer on Simple interest

 9 If an amount Rs. 8000 becomes to Rs. 9200 in 3 years at simple interest. If the rate of interest is increased by 3%, it would amount to A.    Rs.9920 B.    Rs.10560 C.    Rs.11120 D.    Rs.11820 Answer : A.  Rs.9920 Explanation:         Principal = Rs. 8000,                 S.I. = Rs. 1200,                Time = 3years  $\dot{..}$            Rate = $\bigg({100 \times 1200 \over 8000 \times 3} \bigg)$%                        =5 %         New rate  =8 %, Principal = Rs. 8000, Time = 3 years                   S.I = Rs. $\bigg({8000 \times 8 \times3 \over 100} \bigg)$                        =Rs. 1920 $\dot{..}$ New amount = Rs. (8000+1920)                        =9920 Discuss 10 Rajnish took a loan for 7 years at the rate of 6% p.a. S.I. if the total interest paid was Rs.2100, The principal was A.    Rs.4400 B.    Rs.4800 C.    Rs.5000 D.    Rs.5200 Answer : C.  Rs.5000 Explanation: Principaal = Rs. $\Bigg( {2100 \times 100 \over 7 \times6} \Bigg)$                =Rs. $\Bigg( {300 \times 100 \over 6} \Bigg)$                =Rs. 5000 Discuss 11 Mr. Santosh finds that an increase in the rate of interest from $4{7 \over8}$% to $7{3 \over 4}$%, his yearly income diminishes by Rs.615. His capital is A.    Rs.260000 B.    Rs.246000 C.    Rs.238000 D.    Rs.224000 Answer : B.   Rs.246000 Explanation: Let capital be Rs. x. Then ${x \times 8 \times 1 \over 100}-x{31 \over 4} \times {1 \over 100} =615$ or   $32x-31x=61500 \times 4$ $\dot{..}$      x= 246000. Discuss 12 A sum of money was lent at simple interest at 11% p.a. for $3{1 \over 2}$years and $4{1 \over 2}$ years respectively. If the difference in interests for periods was Rs. 5500, then the sum is A.    Rs.50050 B.    Rs.55000 C.    Rs.50000 D.    Rs.50500 Answer : C.  Rs.50000 Explanation: Let the sum Rs.x. Then  $\Bigg( x\times 11 \times {9 \over 2} \times {1 \over 100} -x \times 11 \times {7 \over 2} \times {1 \over 100}\Bigg)$= 5500 or            ${22x \over 200 }=5500$ or           $11x=550000$ or              $x=50000.$ Discuss 13 How much should money lender lend at simple rate of interest of 15% in order to have Rs. 3234 at the end of $1{1 \over 2}$ years ? A.    Rs. 1640 B.    Rs.2620 C.    Rs. 2610 D.    Rs.2640 Answer : D.  Rs.2640 Explanation: Let the required money be x. Then          $\Bigg( x+{x \times 15 \over 100} \times {3 \over 2} \Bigg)=3234$ or  $49x \over 40$=3234 or  $x = \bigg({3234 \times 40 \over 49 }\bigg)=2640$ Discuss 14 What annual payment will discharge a debit of Rs. 1740 due in 5 years, the rate being 8% per annum ? A.    Rs. 360 B.    Rs. 300 C.    Rs. 320 D.    Rs. 340 Answer : B.   Rs. 300 Explanation: Let annual instalment be Rs. x . Then $\bigg[x+\bigg({x \times 4 \times 8 \over100}\bigg) \bigg ]+ \bigg[x+\bigg({x \times 3 \times 8 \over100}\bigg) \bigg ]+$ $\bigg[x+\bigg({x \times 2 \times 8 \over100}\bigg) \bigg ]+\bigg[x+\bigg({x \times 1 \times 8 \over100}\bigg) \bigg ]+x$=1740 Or  ${33x \over25}+{31x \over25}+{29x \over25}+{27x \over25}+x=1740$ Or  $x=300$ Discuss 15 A sum of Rs. 1000 is lent to be returned in 11 monthly installments of Rs. 100 each , interest being simple. The rate of interest is  A.    $9{1\over 11}\%$ B.    $10\%$ C.    $11\%$ D.    $21{9\over 11}\%$ Answer : D.  $21{9\over 11}\%$ Explanation: Rs. 1000+S.I. on Rs. 1000 for 11 months   = Rs. 1000+S.I on Rs. 100 for (1+2+3+4+....+10) months  Rs. 1000 S.I on Rs. 100. for $110 \over 2$ months = Rs. 1000+S.I.on Rs. 100 for 55 months S.I. on Rs. 100 for 55 months = Rs. 100. $\dot{..}$         Rate = $\bigg({1000 \times 100 \times 12 \over 100 \times 55 } \bigg) \% = 21{9\over 11}\%$   Discuss 16 Rajan Lent Rs. 1200 to Rakesh for 3 years at a certain rate of ssimple interest and Rs. 1000 to Mukesh for the same time at same rate. If he gets Rs. 50 More from Rakessh thaan Mukesh, Then the rate percent is. A.    $8{1\over 3}\%$ B.    $6{2\over3}\%$ C.    $10{1\over 3} \%$ D.    $9{3\over2}\%$ Answer : A.  $8{1\over 3}\%$ Explanation: ${1200 \times R \times 3 \over 100 }-{1000 \times R \times 3 \over 100 }=50$ or   $6R=50$ or   $R=8{1 \over 3}\%$ Discuss