Simple Interest- Aptitude Questions and Answers

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A sum of money doubles in 10 years. In how many years will it become four times at the same rate of simple interest?

A)
30 years

B)
50 years

C)
20 years

D)
25 years


Correct Answer :

30 years


Explanation :

Let Principal = P, Rate = R% per annum, Time = n years.
Simple Interest (SI) = (P*R*T )/100

money doubles in 10 years then, 2P=P+(P*R*10 )/100
P=(P*R )/10
R=10

it become four times at the same rate then, 4P=P+(P*10*T )/100
3P=(P*T )/10
So, T=30

A principle becomes twice in 5 years. In how many years it will become 10 times?

A)
45 years

B)
25 years

C)
50 years

D)
None of these


Correct Answer :

45 years


Explanation :

A = P(1 + rt/100)
P = principal
r = rate in %
t = time in years

A principle becomes twice in 5 years, that is
A= 2P, T=5 ,R=?
2P= P + PR * 5/100
2P-P = PR/20
P= PR/20
R= 20
now when the money 10 times, that is
A= 10P , R= 20 , T=?
10P = P + PRT/100 = P + P * 20 * T /100
10P-P = PT/5
9P = PT/5
T= 45
After 45 years the money becomes 10 times

If a sum becomes Rs.18300 in 15/2 years at the rate of 7% per annum, find the sum?

A)
Rs. 10000

B)
Rs. 12000

C)
Rs. 14000

D)
Rs. 15000


Correct Answer :

Rs. 12000


Explanation :

Simple Interest (SI) = (P*R*T )/100
Amount, A = P + SI = P + (P*R*T)/100

Let the Orignal amount is P then ,R=7 and T= 15/2 years
18300 = P +[P* 7* (15/2) /100 ]
18300 = P + [ (P* 7* 15) / 200 ]
18300 = P + [ 21*P / 40 ]
61*P=18300 * 40
P=300*40
P=12000
Hence the Amount was 12000

Find the sum of money will amount to Rs 900 in 4 years at 5 % per annum on simple interest?

A)
Rs 750

B)
Rs 650

C)
Rs 500

D)
Rs 550


Correct Answer :

Rs 750


Explanation :

Let Principal = P, Rate = R% per annum, Time = n years.
Simple Interest (SI) = (P*R*T )/100

Amount =P + (P*R*T )/100

Thus, 900 = P + (P*5*4 )/100
⇒ 900 = 6*P / 5
⇒ P = ( 900 x 5) /6
= Rs 750

At what rate percent per annum will a sum of money doubles in 8 years?

A)
12 %

B)
12.5 %

C)
13 %

D)
15 %


Correct Answer :

12.5 %


Explanation :

Let Principal = P, Rate = R% per annum, Time = n years.
Simple Interest (SI) = (P*R*T )/100

Amount =P + (P*R*T )/100
Thus, 2P =P + (P*R*8 )/100
⇒ P= P*R*8 / 100
⇒ R = 100 /8
So, R=12.5%

A sum of money amounts to Rs. 702 in 2 years and Rs. 783 in 3 years. The rate percent is ?

A)
12% per annum

B)
13% per annum

C)
14% per annum

D)
15% per annum


Correct Answer :

15% per annum


Explanation :

Let Principal = P, Rate = R% per annum, Time = n years.
Simple Interest (SI) = (P*R*T )/100

S.I. for 1 year = Rs. (783 - 702) = Rs 81
S.I. for 2 years = Rs. (81 x 2) = Rs. 162
Then, Sum P = Rs. (702 - 162) = Rs. 540
So, Required rate R =(100 x SI) / (P x T) = (100 x 162) / (540 x 2) % = 15%

Rahul borrowed Rs. 8000 from Mr. Chobey at simple interest. After 2 years he paid Rs. 800 more than what be borrowed and thus cleared the loan. What was the rate of interest ?

A)
6

B)
8

C)
5

D)
None of these


Correct Answer :

5


Explanation :

Let Principal = P, Rate = R% per annum, Time = n years.
Simple Interest (SI) = (P*R*T )/100

Then, Rate R = (SI x 100) / (P*T)
= (800 x 100) / (8000 x 2)
= 5%

Deepak invested an amount of 21250 for 6 yr. At what rate of simple interest, will he obtain the total amount of 26350 at the end of 6 yr ?

A)
4% pa

B)
5% pa

C)
8% pa

D)
12% pa


Correct Answer :

4% pa


Explanation :

Let Principal = P, Rate = R% per annum, Time = n years.
Simple Interest (SI) = (P*R*T )/100

Then, SI = 26350 - 21250 = 5100
R= (SI x 100) / (P * T)
= (5100 x 100) / (21250 x 6)
So, Rate R= 4%

A sum of Rs.3900 is lent out in two parts in such a way that the simple interest on one part at 10% for 5 years is equal to that on another part at 9% for 6 years. Find the sums.

A)
1950, 1950

B)
2025, 1875

C)
1800, 2100

D)
1950, 1800


Correct Answer :

2025, 1875


Explanation :

Let Principal = P, Rate = R% per annum, Time = n years.
Simple Interest (SI) = (P*R*T )/100

Let, Principle lent out in two parts as x and 3900-x
Then As given,

x * 10* 5= (3900-x) * 9 * 6
25x = 3900*27 - 27x
52x=3900*27
x=2025

other part is x=2025
other part is 3900-x = 3900-2015 =>1875

The sum which amounts to Rs.889 in 3 years at the rate of 9% per annum simple interest is Rs._____?

A)
700

B)
800

C)
600

D)
160


Correct Answer :

700


Explanation :

Simple Interest (SI) = (P*R*T )/100
Amount, A = P + SI = P + (P*R*T)/100

Let the Orignal amount is P then ,
889 = P +( P* 9* 3)/100
127*P=889*100
P=88900/127
P=700
Hence the Amount was 700

Mr. Thomas invested an amount of Rs. 13,900 divided in two different schemes A and B at the simple interest rate of 14% p.a. and 11% p.a. respectively. If the total amount of simple interest earned in 2 years be Rs. 3508, what was the amount invested in Scheme B?

A)
7000

B)
6500

C)
6400

D)
6000


Correct Answer :

6400


Explanation :

Let the sum invested in Scheme A be Rs. x , And that in Scheme B be Rs. (13900 - x).
Then, [(x * 14 * 2) / 100] + {[(13900 - x) * 11 * 2] / 100 } = 3508
(28x / 100) + [(13900 - x) * 22] / 100 = 3508
28x + [(13900 - x) * 22] = 3508 * 100
28x + [(13900 - x) * 22] = 350800
28x + 305800 – 22x = 350800
28x – 22x = 350800 – 305800
6x = 45000
x = 7500
So, sum invested in Scheme B = Rs. (13900 – 7500) = Rs. 6400

Two equal amount were lent on simple interest of 7% and 5% respectively. The interest earned on both of them adds 960 rupees in 4 years. What is the total amount lent out?

A)
3500

B)
2500

C)
2000

D)
3000


Correct Answer :

2000


Explanation :

Let the amount is X

As is given, (X*7*4 / 100) + (X*5*4 / 100) =960
28*X/100 + 20*X/100= 960
X=960*100 / 48 =2000

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