The average of 8 numbers is 20. The average of first two numbers is $$15\frac{1}{2}$$ and that of the next three is $$21…

A library has an average of 510 visitors on Sundays and 240 on other days. The average number of visitors per day in a m…

The average age of a class of 39 students is 15 years. If the age of the teacher is included, then the average increases…

Out of 20 boys, 6 are each of 1 m 15 cm height, 8 are of 1 m 10 cm and rest of 1 m 12 cm. The average height of all of t…

The arithmetic mean of the following numbers : 1, 2, 2, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6 and 7, 7, 7…

The average of X<sub>1</sub>, X<sub>2</sub> and X<sub>3</sub> is 14. Twice the sum o…

Distance between two stations A and B is 778km. A train covers the journey from A to B at 84km per hour and returns back…

The average of a collection of 20 measurements was calculated to tb 56 cm. But later it was found that a mistake had occ…