Question

a person invests Rs5000 at 5% p.a simple interest for a certain period and earns Rs 750. If he earns Rs.720 on Rs.6000 in the same time period then what is the rate of interest?

Answer 1

This question is purely based on the simple interest formula.

We have SI = $\frac{PTR}{100}$

where
'SI' stands for Simple Interest
'P' stands for Principal Amount
'T' stands for Time
'R' stands for Rate Of Interest

We are given that the principal is Rs. 5000, rate is 5% and interest is Rs. 750. Thus, we can find the time.

750 = $\frac{5000*T*5}{100}$
750 = 50*T*5
750 = 250 T
Thus, T = $\frac{750}{250}$ = 3
Hence, the time is 3 years (as the rate of interest is given in 'per annum').

Now, using this, we move on to the next part of the question. It says that principal is Rs. 6000, time is same i.e. 3 years and interest is Rs. 720. We need to find the rate of interest.

Using the same formula,

720 = $\frac{6000*3*R}{100}$
720 = 60 * 3 * R
720 = 180 R
R = 4

Hence, the rate of interest is 4% per annum.

Answer 2

Step-by-step explanation:

For the invest of 5000 Rs

I= PTR/100

750=5000*T*5/100

T=750*100/5000*5

T=3 Years

For the invest of 6000 Rs

I=PTR/100

720=6000*3*R/100

R=720*100/6000*3

R=72/18

R=4

The rate of intrest is 4%