Family income average: A family has 4 earning members with an average monthly income of Rs 735. After one member passes away, the average for the remaining 3 becomes Rs 650. Find the monthly income of the deceased member.

Introduction / Context:
This is a direct average to total conversion problem. Knowing the average and count allows recovery of totals and the missing value.

Given Data / Assumptions:

• Initial earners = 4, average = Rs 735
• After one leaves, earners = 3, average = Rs 650

Concept / Approach:
Total = average * count. Income of the deceased = initial total - new total.

Step-by-Step Solution:

Verification / Alternative check:
Average with all four: 2940/4 = 735. Removing 990 leaves 1950 for 3, which averages to 650. Checks out.

Why Other Options Are Wrong:

• Rs 692.80, Rs 820, Rs 1385: Do not match the difference between totals computed from the given averages.

Common Pitfalls:
Confusing averages with totals and attempting to average averages directly without weighting by counts.

Final Answer: