“In a supermarket, the first 25 customers of the day purchased an average of two items each.
After a further 15 customers, the average number of items purchased by each customer rose to eight.
What was the average number of items purchased by the last 15 customers only?”
Answer: 18

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“A vehicle has travelled 50 miles at  50 mph.
It started its journey with 8 gallons of fuel but its tank has been leaking throughout the journey and is now dry.
The vehicle completes 40 miles per gallon.
How many gallons of fuel does it leak per hour?”
Answer: 6,75