A and B invest Rs 3000 and Rs 2400 respectively in a business. After one year, the business makes a total loss of Rs 720. Assuming that loss is shared in proportion to their investments, how much loss will B bear?

Introduction / Context:
This is a partnership and loss distribution question. In business partnerships, both profits and losses are usually shared in the ratio of the investments made by each partner, provided there is no separate agreement about sharing. Here we need to determine B's share of the total loss based on the ratio of amounts invested by A and B.

Given Data / Assumptions:
- A invests Rs 3000. - B invests Rs 2400. - Total loss after one year = Rs 720. - Loss is assumed to be shared in the ratio of their investments.

Concept / Approach:
When no special conditions are mentioned, the share of each partner in profit or loss is proportional to the amount invested and the time period for which it is invested. Here time is the same for both, so we only use the investment amounts. We find the ratio of investments, then apply that ratio to the total loss to get each partner's share.

Step-by-Step Solution:
Step 1: Investment by A = 3000, by B = 2400. Step 2: Ratio of investments = 3000 : 2400. Step 3: Divide both terms by 600 to simplify: 3000 / 600 = 5, 2400 / 600 = 4, so ratio = 5 : 4. Step 4: Total parts in this ratio = 5 + 4 = 9. Step 5: Total loss = Rs 720, so one part = 720 / 9 = Rs 80. Step 6: B's share of loss = 4 parts = 4 * 80 = Rs 320.

Verification / Alternative check:
Check that A's share of loss is 5 * 80 = Rs 400. Then A's loss plus B's loss = 400 + 320 = 720, which matches the total loss. Also note that A's share is larger because he invested more, which matches the logical expectation.

Why Other Options Are Wrong:
Option Rs. 72 is far too low and would not add up correctly to the total loss when combined with A's share. Option Rs. 400 matches A's share, not B's, so it is incorrect for the question asked. Option Rs. 360 corresponds to a wrong distribution ratio and would imply an incorrect investment ratio.

Common Pitfalls:
A typical mistake is to divide the total loss equally between A and B, ignoring the investment ratio. Another error is to invert the ratio or to forget to simplify the ratio correctly before applying it. Always compute the ratio first, find the sum of ratio parts, and then allocate the profit or loss.

Final Answer:
B will bear a loss of Rs 320.