Five boxes of bananas sell for Rs 30. At this rate, how many boxes of bananas can be bought for Rs 9?

Introduction:
This is a simple unitary method question dealing with direct proportion between quantity and price. If five boxes of bananas cost Rs 30, you need to find how many boxes can be purchased for Rs 9 at the same rate.

Given Data / Assumptions:
Cost of 5 boxes of bananas = Rs 30. We assume the price per box is constant. We need to find the number of boxes that can be bought for Rs 9.

Concept / Approach:
In direct proportion, if cost increases, the number of boxes increases in the same ratio. The steps are: 1. Find the cost of one box. 2. Use that cost to find how many boxes can be purchased for Rs 9. Alternatively, directly use ratios between cost and number of boxes.

Step-by-Step Solution:
Step 1: Find price per box. 5 boxes cost Rs 30. Price per box = 30 / 5 = Rs 6. Step 2: Find boxes that can be bought for Rs 9. Number of boxes = 9 / 6. Number of boxes = 1.5.

Verification / Alternative Check:
Another way: Consider the ratio of costs and quantities. If 30 rupees gives 5 boxes, 9 rupees is 9 / 30 = 0.3 of the original cost. 0.3 of 5 boxes = 5 * 0.3 = 1.5 boxes, which matches our calculation.

Why Other Options Are Wrong:
2 and 2.5 boxes: These would correspond to spending Rs 12 or Rs 15 at Rs 6 per box, not Rs 9. 1.25 and 1: These would cost Rs 7.50 and Rs 6 respectively, which do not match the given budget of Rs 9.

Common Pitfalls:
Some learners mistakenly divide 5 by 30 instead of 30 by 5 to get the price per box. Others may forget to maintain consistent units or approximate 9 / 6 incorrectly. Always compute the unit price carefully and then use it for the required amount.

Final Answer:
At the given rate, the man can buy 1.5 boxes of bananas for Rs 9.