Interest - Study Mode
[#16] A sum is deposited in a bank which gives simple interest. The sum becomes 1.25 times in 3 years. If there is a requirement of Rs. 7,60,000 after seven years, how much amount (in Rs.) should one deposit to fulfil the requirement?
Correct Answer
(C) 4,80,000
Explanation
Solution: Let the sum = 100 $$eqalign{
& { ext{Rate}} = frac{{25}}{3}\% cr
& Rightarrow { ext{Total amount in}} cr
& = 100 + frac{{25}}{3} imes 7 cr
& = 100 + frac{{175}}{3} cr
& = frac{{475}}{3}mu o 76000 cr
& 1mu o 4800 cr
& 100mu o 480000 cr} $$
[#17] A certain sum is lent at 4% per annum for 3 years 8% per annum for next 4 years and 12% per annum beyond 7 years. If for a period of 11 years, the simple interest obtained is Rs. 27,600, then the sum is (in Rs.):
Correct Answer
(D) 30,000
Explanation
Solution: $$eqalign{
& 27600 = frac{{Pleft( {3 imes 4 + 4 imes 8 + 4 imes 12}
ight)}}{{100}} cr
& frac{{27600 imes 100}}{{12 + 32 + 48}} = P cr
& P = frac{{27600 imes 100}}{{92}} cr
& P = { ext{Rs}}{ ext{. }}30000 cr} $$
[#18] If the amount obtained by A by investing Rs. 9,100 for three years at a rate of 10% p.a. on simple interest is equal to the amount obtained by B by investing a certain sum of money for five year at a rate of 8% p.a. on simple interest, then 90% of the sum invested by B (in Rs.) is:
Correct Answer
(D) 7,605
Explanation
Solution: Amount obtained by A is equal to amount obtained by B Amount = Principal + Simple Interest $$eqalign{
& 9100 + frac{{9100 imes 10 imes 3}}{{100}} = B + frac{{B imes 8 imes 5}}{{100}} cr
& 9100 + 2730 = frac{{140}}{{100}}B cr
& B = 11830 imes frac{{100}}{{140}} cr
& B = 8450 cr} $$ 90% of invested amount by B $$eqalign{
& = 8450 imes frac{{90}}{{100}} cr
& = 7605 cr} $$
[#19] A person deposited Rs. 15,600 in a fixed deposit at 10% per annum
simple interest. After every second year he adds his interest earned to
the principal. The interest at the end of 4 years is:
Correct Answer
(B) Rs. 6,864
Explanation
Solution: $$eqalign{
& { ext{S}}{ ext{.I}}{ ext{. for 2 years}} cr
& = frac{{15600 imes 2 imes 10}}{{100}} cr
& = 3120 cr
& { ext{Principal for next 2 years}} cr
& = 15600 + 3120 cr
& = 18720 cr
& { ext{S}}{ ext{.I}}{ ext{. for next 2 years}} cr
& = frac{{18720 imes 10 imes 2}}{{100}} cr
& = 3744 cr
& { ext{Total S}}{ ext{.I}}{ ext{.}} cr
& = 3120 + 3744 cr
& = 6864 cr} $$
[#20] A person borrowed 1,200 at 8% per annual and Rs. 1,800 at 10% per annum, as simple interest for the same period. He had to pay Rs. 1380 in all as interest. Find the time? (in year)
Correct Answer
(B) 5 years
Explanation
Solution: $$eqalign{
& frac{{1200 imes t imes 8}}{{100}} + frac{{1800 imes t imes 10}}{{100}} = 1380 cr
& 96t + 180t = 1380 cr
& 276t = 1380 cr
& t = 5 cr} $$