Question

9/15 A sum amounts to Rs. 64500 and Rs. 75400 after 2 years and 7 years respectively, at Sl. What will be the amount at the end of 12 years?​

Answer 1

Answer:

Solution

Let Rs P be the sum and R % be the rate of interest per annum. 

Given, 

Amount in 4 years = Rs. 5600 

⇒P(1+4R100)=5600⇒P(1+4R100)=5600 

Also, amount in 6 years =Rs. 6400 

⇒P(1+6R100)=6400⇒P(1+6R100)=6400 

(1)+(2) gives, 

1+4R1001+6R100=56006400⇒100+4R100+6R=781+4R1001+6R100=56006400⇒100+4R100+6R=78 

⇒8(100+4R)=7(100+6R)⇒8(100+4R)=7(100+6R) 

⇒10R=100⇒R=10⇒10R=100⇒R=10 

On substituting R=10 in (1), we get, 

P(1+40100)=5600⇒7P5=5600⇒P=4000P(1+40100)=5600⇒7P5=5600⇒P=4000

Hence, the requied sum is Rs. 4000 and the rate of interest is 10% per annum.