A batsman has played 80 innings and has an average of 99 runs. In the most recent (80th) innings he scored 0. To end with an average of 100 after 80 innings, what should his score in the last innings have been?

Introduction:
Target-average questions are solved by total runs logic. To average 100 after 80 innings, the total must be 80 * 100. Compare this requirement with the actual total given the existing average and adjust for the last innings score needed.

Given Data / Assumptions:

• Innings count = 80
• Current average = 99 → current total = 80 * 99
• Desired average = 100 → required total = 80 * 100
• We substitute the last-innings score so that total meets the requirement.

Concept / Approach:
Required last score = required total − (current total − last actual score). Since the last actual score is 0, the difference of totals itself is the needed score.

Step-by-Step Solution:

Verification / Alternative check:
If he had made 80, his final total would be 8000, giving 8000/80 = 100 exactly.

Why Other Options Are Wrong:
60, 40, 10, or 1 do not bridge the 80-run gap between totals needed and totals achieved.

Common Pitfalls:
Averaging 99 and 100 or trying to add 1 directly to the average without using totals. Always compute totals first.

Final Answer:
80 runs