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# Discussion

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 ?

• A.2010
• B.2011
• C.2012
• D.2013

Suppose commodity X will cost 40 paise more than Y after z years.
Then,
$$(4.20 + 0.40z) - (6.30 + 0.15z) = 0.40\\ \Rightarrow 0.25z = 0.40 + 2.10\\ \Rightarrow z= \dfrac {2.50}{0.25} = \dfrac {250}{25} = 10$$

X will cost 40 paise more than Y 10 years after 2001 i.e., 2011

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