Simple Interest Questions -01

In this post we will solve questions of Simple Interest chapter of Quantitative Aptitude. The questions of this chapter is not that difficult but you have to spend some tie practicing its questions so that you can solve its question as quickly as possible in examination hall.

In this post you will find questions related to calculation of Simple Interest Principal and Rate of Interest which have been repeatedly asked in competition exams that’s why all the questions are important and need suitable time investment.

Simple Interest Questions

(01) A sum of money become 7/6 of itself in 3 years at a certain rate of simple interest. Find the rate of interest per annum

Principal = x,
Amount = 7x/6,
Simple Interest = 7x/6 – x = x/6

100x = 6 × x × R × 3

R =100/ (6*3)  = 50/9%

Hence the rate of interest is 50/9 % per annum

(02) The simple interest on a certain sum at 5% per annum for 3 years and 4 years differ by Rs. 42. Find the principal amount

Sol:
Let the principal be x.
Rate 1 =5 %
Time 1 = 3 years
Rate 2 =5 %
Time 2 = 4 years

According to question:
The simple interest for 4 years and 3 years differ by Rs. 42

5x/100 = 42

x = 100 × 42 / 5 = Rs. 840

Hence Rs. 840 is the principal amount

(03) A sum of Rs. 10,000 is lent partly at 8% and remaining at 10% per annum. If the yearly interest on the average is 9.2%, find the two parts of the principal.

Let us divide Rs. 10000 into two parts x and 10000-x
Rs. x is lent at 8% and 10000-x is lent at 10% per annum

So,
P1 = x
R1 = 8%
T1= 1 year

P2=10000-x
R2=10%
T2= 1 year

As per the question, the yearly interest on average is 9.2%

According to question,

8x + 100000 – 10x = 92000

-2x = -8000

x = 4000

First part = Rs. 4000 and Second part = Rs. 6000

Hence the first part of principal is Rs. 4000
And second part of principal is Rs. 6000

(04) A sum of Rs. 400 amounts to Rs. 480 in 4 years. What will it amount to if the rate of interest is increased by 2%?

Principal= Rs. 400
Amount = Rs. 480

SI = Rs. (480 – 400) = Rs. 80

New Rate = 5 + 2 = 7%

New amount = Rs. ( 400 + 112 ) = Rs. 512

Hence when rate is increased by 2%, the new amount will be rs 512

Let the first part = x, then the second part = 1750 – x

P1=> x
R1=> 8%

P2 => 1750-x
R2 => 6%

As per question, the interest in first part and second part is equal

x × 8/100 × 1 = ( 1750 – x ) × 6/100 × 1

x = 750

First part = Rs. 750 and Second part = Rs. 1750 – Rs. 750 = Rs. 1000

Interest on each part = 750 × 8/100 = Rs. 60

First part = x and Second part = 5000 – x

P1= x
R1= 4%
T1 = 2 years

P2 =5000-x
R2 = 5%
T2 = 2 years

According to question:

-2x = 44000 – 50000

-2x = -6000

x = 3000

First part = 3000 and Second part = 5000 – 3000 = 2000

Required ratio = 3000 : 2000 = 3 : 2

Let the capital be Rs. x

Initial Rate of Interest
P1 =x
R1 = 8%

When rate of interest changes
P2= x
R2 =31/4%

According to question

x = 61.50 × 400 = Rs. 24,600

Hence the initial capital of money lander was Rs. 24,600

Interest From B
P1= 2500 rs
R1 = 7%
T1 = 4 years

Interest From C
P2 = Rs x
R2 = 7%
T2 = 4 Years

2500 + x = 4000

x = 4000 – 2500 = 1500

Hence, the sum lent to C is 1500 Rs

Let the sum be P.

R1 = 4%
T1 = 8 Months

R2= 5%
T2 = 15 Months

According to question

Hence Rs 3600 is the initial principal amount

Let the principal be Rs P
R1 = 11.5%
T1 = 1 year

R2= 10%
T2 = 1 year

According to question

11.5P – 10P = 5550

P = 5550 / 1.5 = Rs. 3700

Hence 3700 rs is the initial capital