Two block averages combined: A car consumes on average 110 litres of petrol per month for the first 7 months and 86 litres per month for the next 5 months. Find the average monthly consumption for the full year.

Introduction / Context:Weighted averages by month counts give the yearly mean consumption.Given Data / Assumptions:

• First 7 months average = 110 litres
• Next 5 months average = 86 litres

Concept / Approach:Compute total litres in each block, add them, then divide by 12 months.Step-by-Step Solution:

Verification / Alternative check:Proportional weighting by 7 and 5 months is correctly applied.Why Other Options Are Wrong:

• 96, 98, 102 litres: Do not equal the exact weighted result.

Common Pitfalls:Taking a simple mean of 110 and 86 without weighting by month counts.Final Answer: