Simple Interest
Simple Interest
Simple Interest
SIMPLE INTEREST
SOLVED EXAMPLES
Ex. 1. Find the simple interest on Rs. 68,000 at 16 2/3% per annum for 9 months.
( )
∴ S.I. = (P*R*T)/100 = Rs. 68,000*(50/3)*(3/4)*(1/100) = Rs.8500
Ex. 2. Find the simple interest on Rs. 3000 at 6 1/4% per annum for the period from
( )
∴ S.I. = Rs. 3,000*(25/4)*(1/5)*(1/100) = Rs.37.50.
Remark : The day on which money is deposited is not counted while the day on which
money is withdrawn is counted .
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Sol. Let sum be Rs. x then , S.I.=Rs. x*(27/2) *4*(1/100) ) = Rs.27x/50
( )
∴ amount = Rs. x+(27x/50) = Rs.77x/50
∴ 77x/50 = 2502.50 ⇔ x = 2502.50 * 50 = 1625
77
Hence , sum = Rs.1625.
Ex. 4. A sum of Rs. 800 amounts to Rs. 920 in 8 years at simple intere
interest rate is increased by 8%, it would amount to bow mucb ?
Sol. S.l. = Rs. (920 - 800) = Rs. 120; p = Rs. 800, T = 3 yrs. _
(
. R = (100 x 120)/(800*3) ) % = 5%.
New rate = (5 + 3)% = 8%.
New S.l. = Rs. (800*8*3)/100 = Rs. 192.
: New amount = Rs.(800+192) = Rs. 992.
Ex. 5. Adam borrowed some money at the rate of 6% p.a. for the first two years , at the
rate of 9% p.a. for the next three years , and at the rate of 14% p.a. for the period
beyond five years. 1£ he pays a total interest of Rs. 11, 400 at the end of nine years how
much money did he borrow ?
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⇔ 3x/25 + 27x/100 + 14x / 25 ) = 11400 ⇔ 95x/100 = 11400 ⇔ x = (11400*100)/95
= 12000.
Ex. 6. A certain sum of money amounts to Rs. 1008 in 2 years and to Rs.1164 in 3 ½
years. Find the sum and rate of interests.
Ex. 8. The simple interest on a sum of money is 4/9 of the principal .Find the rate
percent and time, if both are numerically equal.
Ex. 9. The simple interest on a certain sum of money for 2 l/2 years at 12% per
annum is Rs. 40 less tban the simple interest on the same sum for 3 ½ years at 10% per
annum. Find the sum.
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Sol. Let the sum be Rs. x Then, (x*10*7)/(100*2) ) – ( (x*12*5)/(100*2)) = 40
⇔ (7x/20)-(3x/10)=40
⇔x = (40 * 20) = 800.
Ex. 10. A sum was put at simple interest at a certain rate for 3 years. Had it been
put at 2% higher rate, it would have fetched Rs. 360 more. Find the sum.
Ex. 11. What annual instalment will discharge a debt of Rs. 1092 due in 3 years
at 12% simple interest?
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Sol .Let each Instalment be Rs. x
Ex. 12. A sum of Rs. 1550 is lent out into two parts, one at 8% and another one at
6%. If the total annual income is Rs. 106, find the money lent at each rate.
Sol. Let the sum lent at 8% be Rs. x and that at 6% be Rs. (1550 - x).
)
∴ ((x*8*1)/100) + ((1550-x)*6*1 /100=106
⇔8x + 9300 –6x=10600 ⇔ 2x = 1300 ⇔ x = 650.
∴ Money lent at 8% = Rs. 650. Money lent at 6% = Rs. (1550 - 650) = Rs. 900.