The average monthly consumption of petrol for a car for the first 7 months of a year is 330 litres, and for the next 5 months is 270 liters. What is the average consumption per month during the whole year?
Average monthly consumption of petrol for 7 months = 330 liters
Total consumption for 7 months = 7×330 = 2310 liters
Average consumption for next 5 months = 270 liters
Total consumption for next 5 months = 5×270 = 1350 liters
Total consumption during whole year = 2310 + 1350 = 3660 liters
Now,
Average consumption per month during whole year = 
= 305 liter/per month
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