Q13 of 32 Page 46

At the same rate of simple interest in percent per annum, if a principal becomes the amount of ₹7100 in 7 yrs. and of ₹6200 in 4 yrs., let us determine the principal and rate of simple interest in percent per annum.

Case 1:


Amount = Principal + Interest


P = p, r = ?, t = 7 yrs and I = I


As we know,





⇒ Rs. 7100



Case 2:


P = p, r = ?, t = 4 yrs and I = I


As we know,





Amount = Principal + Interest


⇒ Rs. 6200 = p +



Dividing the above equations we get,




⇒ 7100 + 284r = 6200 + 434r


⇒ 900 = 150r



To find the value of principal putting the value of r in any equation


⇒7100 =


⇒ p = = Rs. 5000


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