Question 1

At what rate percent per annum will a sum of money double in 8 years.

Accepted Answer

Let principal = P, Then, S.I.= P and Time = 8 years We know that S.I. = PTR/100 Rate = [(100 x P)/ (P x 8)]% = 12.5% per annum.

Question 2

A sum of money at simple interest amounts to Rs. 815 in 3 years and to Rs. 854 in 4 years. The sum is:

Accepted Answer

S.I. for 1 year = Rs. (854 - 815) = Rs. 39. S.I. for 3 years = Rs.(39 x 3) = Rs. 117. Principal = Rs. (815 - 117) = Rs. 698

Question 3

What annual instalment will discharge a debt of Rs 1092 due in 3 years at 12% simple interest?

Accepted Answer

Let each instalment be Rs.x . 1st year = [x + (x * 12 * 2)/100] 2nd year = [ x + (x *12 * 1)/100] 3rd year = x Then, [x + (x * 12 * 2)/100] + [ x + (x *12 * 1)/100] + x =1092 3x + ( 24x/100 ) + ( 12x/100 ) = 1092 336x =109200 Therefore, x = 325 Each instalment = Rs. 325

Question 4

In how many years will a sum of Rs.800 at 10% per annum compounded semi annually become Rs.926.10

Accepted Answer

Let the time be 'n' years, Then 800 × 1 + 5 100 2 n = 926 . 10 < = > 1 + 5 100 2 n = 9261 8000 < = > 21 20 2 n = 21 10 3 n = 3/2 or n= 1 1 2 Years

Question 5

A man took loan from a bank at the rate of 12% p.a. simple interest. After 3 years he had to pay Rs. 5400 interest only for the period. The principal amount borrowed by him was:

Accepted Answer

Principal = R s 100 × 5400 12 × 3 = R s . 15000

Question 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 the rate of interest.

Accepted Answer

S.I. for 1 ½ years = Rs (1164 - 1008) = Rs 156 . S.I. for 2 years = Rs (156 x 2 3 x 2)= Rs 208. Therefore, Principal = Rs (1008 - 208) = Rs 800. Now, P = 800, T= 2 and S.I. = 208. Therefore, Rate = (100 x S.I.) / (P x T) = [ (100 x 208)/(800 x 2)]% = 13%

Question 7

Simple interest on a certain sum is 16/25 of the sum. Find the rate percent and time, If both are numerically equal.

Accepted Answer

Let sum = X. Then S.I = 16x/25 Let rate = R% and Time = R years. Therefore, (x * R * R)/100 = 16x/25 => R = 40/5 = 8 Therefore, Rate = 8% and Time = 8 years.

Question 8

A person borrows Rs. 5000 for 2 years at 4% p.a. simple interest. He immediately lends it to another person at 614 p.a for 2 years. Find his gain in the transaction per year

Accepted Answer

g a i n i n 2 y e a r s = R s . 5000 * 25 4 * 2 100 - 5000 * 4 * 2 100 = Rs. (625 - 400) = Rs. 225 g a i n i n 1 y e a r = R s . 225 2 = 112 . 50

Question 9

Find: S.l. on Rs 6250 at 14% per annum for 146 days.

Accepted Answer

P = Rs. 6250, R = 14 % & T = (146/365) years = 2/5 years . S.I= R s . 6250 * 14 * 2 5 100 = R s . 350

Question 10

A sum of Rs.1550 was lent partly at 8% p.a. simple interest. The total interest received after 3 years was Rs.300. The ratio of the money lent at 5% to that lent at 8% is :

Accepted Answer

let the sum lent at 5% be Rs.x and that lent at 8% be Rs.(1550-x). then, Interest on x at 5% for 3 years + interest on (1550-x) at 8% for 3 years = 300 x * 5 * 3 100 + 1500 - x * 8 * 3 100 = 300 x=800 Required ratio = x : (1550-x) = 800 : (1550-800) = 800 : 750 = 16 : 15

Question 11

How much time will take for an amount of Rs. 450 to yield Rs. 81 as interest at 4.5% per annum of simple interest ?

Accepted Answer

Time = (100 x 81) / (450 x 4.5) = 4 years.

Question 12

A certain amount earns simple interest of Rs. 1750 after 7 years. Had the interest been 2% more, how much more interest would it have earned?

Accepted Answer

We need to know the S.I, principal and time to find the rate. Since the principal is not given, so data is inadequate.

Question 13

The difference between the simple interest received from two different sources on Rs.1500 for 3 years is Rs.13.50. The difference between their rates of interest is

Accepted Answer

(1500 x R1 x 3)/100 => 4500 (R1-R2) = 1350 => (R1-R2)= 1350/4500 = 0.3 %

Question 14

A father left a will of Rs.35 lakhs between his two daughters aged 8.5 and 16 such that they may get equal amounts when each of them reach the age of 21 years. The original amount of Rs.35 lakhs has been instructed to be invested at 10% p.a. simple …

Accepted Answer

Let Rs.x be the amount that the elder daughter got at the time of the will. Therefore, the younger daughter got (3,500,000 - x). The elder daughter’s money earns interest for (21 - 16) = 5 years @ 10% p.a simple interest. The younger daughter’s money earns interest for (21 - 8.5) = 12.5 years @ 10% p.a simple interest. As the sum of money that each of the daughters get when they are 21 is the same, x + 5 * 10 * x 100 = 3 , 500 , 000 - x + 12 . 5 * 10 * 3 , 500 , 000 - x 100 x + 50 x = 3 , 500 , 000 - x + 125 100 * 3 , 500 , 000 - 125 x 100 2 x + 50 x 100 + 125 x 100 = 3 , 500 , 000 * 1 + 5 4 200 x + 50 x + 125 x 100 = 9 4 * 3 , 500 , 000 => x = 2 , 100 , 000 = 21 l a k h s

Question 15

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.

Accepted Answer

Let sum = P and original rate = R. Then [(P * (R+2) * 3)/100] - [ (P * R * 3)/100] = 360 3P*(R+2) - 3PR = 36000 3PR + 6P - 3PR = 36000 6P = 36000 P = 6000

Question 16

At what rate of compound interest per annum will a sum of rs.1200 becomes rs.1348.32 in 2 years

Accepted Answer

rate=r% 1200 (1+r/100)^2=1348.32 r=6%

Question 17

A sum of Rs. 725 is lent in the beginning of a year at a certain rate of interest. After 8 months, a sum of Rs. 362.50 more is lent but at the rate twice the former. At the end of the year, Rs. 33.50 is earned as interest from both the loans. What w…

Accepted Answer

Let the original rate be R%. Then, new rate = (2R)%. Note: Here, original rate is for 1 year(s); the new rate is for only 4 months i.e.1/3 year(s). 725 * R * 1 100 + 362 . 50 * 2 R * 1 100 * 3 = 33 . 50 => (2175 + 725) R = 33.50 x 100 x 3 => (2175 + 725) R = 10050 => (2900)R = 10050 => R = 10050 2900 = 3 . 46 Original rate = 3.46%

Question 18

A sum was put at simple interest at a certain rate for 10 years . Had it been put at 5% higher rate , it would have fetched Rs.600 more. What was the Sum?

Accepted Answer

At 5% more rate, the increase in S.I for 10 years = Rs.600 (given) So, at 5% more rate, the increase in SI for 1 year = 600/10 = Rs.60/- i.e. Rs.60 is 5% of the invested sum So, 1% of the invested sum = 60/5 Therefore, the invested sum = 60 × 100/5 = Rs.1200

Question 19

If the C.I. on a sum for 2 years at 12 1/2 % per annum is Rs. 510, the S.I. on the same sum at the same rate for the same period of time is ?

Accepted Answer

Let the sum be Rs. P. Then, P 1 + 25 2 x 100 2 - P = 510 P[ 9 8 2 - 1] = 510. Sum = Rs. 1920 So, S.I. = (1920 x 25 x 2) / (2 x 100) = Rs. 480

Simple Interest Questions