A pineapple costs ₹ 7 each. A watermelon costs ₹ 5 each. X spends ₹ 38 on these fruits. The number of pineapples purchased is
(a)2
(b)3
(c)4
(d)Data inadequate
Answer
Answer (as printed): C
Explanation
Let the number of pineapples and watermelons be $x$ and $y$ respectively. Then, $7 x+5 y=38$ or $5 y=(38-7 x)$ or $y=\frac{38-7 x}{5}$. Clearly, $y$ is a whole number, only when $(38-7 x)$ is divisible by 5. This happens when $x=4$.
Explanation as extracted from the printed page; notation may be imperfect.