The simple interest on a sum of money will be ₹ 600 after 10 years. If the principal is trebled after 5 years, what will be the total interest at the end of the tenth year?
(a)₹ 600
(b)₹ 900
(c)₹ 1200
(d)₹ 1500
(e)Data inadequate
Answer
Answer (as printed): C
Explanation
Let the sum be ₹ $x$. Now, S.I. $=₹ 600, T=10$ years. Rate $=\left(\frac{100 \times 600}{x \times 10}\right) \%=\left(\frac{6000}{x}\right) \%$. S.I. for first 5 years $=₹\left(\frac{x \times 5 \times 6000}{x \times 100}\right)=₹ 300$. S.I. for last 5 years $=₹\left(3 x \times 5 \times \frac{6000}{x \times 100}\right)=₹ 900$. ∴ Total interest $=₹ 1200$.
Explanation as extracted from the printed page; notation may be imperfect.