A certain sum of money becomes Rs. 81000 in 4 years and it becomes Rs. 89373 in 7 years. Find the rate of interest p.a., if compounded annually.
Answer & explanation
Correct answer: option 3
Amt7 = Amt3 (1 + \(\frac{R}{100}\))t
ATQ,
⇒ 89373 = 81000 (1 + \(\frac{R}{100}\))3
⇒ 29791 = 27000 (1 + \(\frac{R}{100}\))3
⇒ \(\frac{29791}{27000}\) = (1 + \(\frac{R}{100}\))3
⇒ (\(\frac{31}{30}\))3 = (1 + \(\frac{R}{100}\))3
⇒ \(\frac{31}{30}\) = (1 + \(\frac{R}{100}\))
⇒ R = \(\frac{100}{30}\) = 3\(\frac{1}{3}\)%