A person borrowed ₹ 500 @ 3\% per annum S.I. and ₹ 600 @ $4 \frac{1}{2} \%$ per annum on the agreement that the whole sum will be returned only when the total interest becomes ₹ 126. The number of years, after which the borrowed sum is to be returned, is :
(a)2 years
(b)3 years
(c)4 years
(d)5 years
Answer
Answer (as printed): B
Explanation
Let the time be $x$ years. Then, $$\left(\frac{500 \times 3 \times x}{100}\right)+\left(\frac{600 \times 9 \times x}{100 \times 2}\right)=126$$ ⇔ $$15 x+27 x=126 \Leftrightarrow 42 x=126 \Leftrightarrow x=3 .$$ $\therefore \quad$ Required time $=3$ years.
Explanation as extracted from the printed page; notation may be imperfect.