The price of commodity X increases by 40 paise every year, while the price of commodity Y increases by 15 paise every year. If in 2001, the price of commodity X was Rs. 4.20 and that of Y was Rs. 6.30, in which year commodity X will cost 40 paise more than the commodity Y ?

Answer: Option B

Suppose commodity X will cost 40 paise more than Y after z years
Then,(4.20 + 0.40z) − (6.30 + 0.15z) = 0.40
⇒ 0.25z = 0.40 + 2.10
$$\begin{array}{rl}& \Rightarrow z=\frac{2.50}{0.25}\\ & =\frac{250}{25}\\ & =10\end{array}$$
∴ X will cost 40 paise more than Y 10 years
After 2001 i.e., 2011