A pineapple costs Rs. 7 each. A watermelon costs Rs. 5 each. X spends Rs.38 on these fruits. The number of pineapples purchased is,
A. 2
B. 3
C. 4
D. data inadequate

Hint: Assume the number of pineapples and watermelons bought to be x & y respectively. Hence, form a linear equation using the given data and solve for them.

Complete step-by-step answer:
Given, cost of a watermelon = Rs. 5.
Cost of a pineapple = Rs. 7.
Total money spent on fruits = Rs. 38.
Let us assume the number of pineapples purchased to be x.
Then, money spent on pineapples is the cost of one pineapple x number of pineapples purchased.
$\Rightarrow $Money spent on pineapples = Rs. 7x
Let us assume the number of watermelons purchased to be y.
Then, money spent on watermelons is the cost of one watermelon times the number of watermelons purchased.
$\Rightarrow $Money spent on watermelon = Rs. 5y
Total money spent = money spent on (watermelons + pineapples)
$\Rightarrow $38 = 7x + 5y.
From the data given, we have two variables but one equation. Therefore, we cannot find a number of pineapples.
Answer is (D) data inadequate.

Note: To solve linear equations of n variables, we need n equations.