WBCS MATHS

Ajit has certain average for 9 innings. In the tenth innings, he scores 100 runs thereby increasing his average by 8 runs. His new average is:

Solve: 100 - (9×8) = 28 years

A man covers half of his journey at 6 km/h and the remaining half at 3 km/h. His average speed is.

Solve:

Trick: When same distance covers twice in different speed,
The average speed = 2×X×Y/X+Y

Here average speed of the man is:
2×6×3/6+3
=2×6×3/9
= 4 km / hour.

A and B together can complete a work in 18 days, A and C together in 12 days, and B and C together in 9 days, then B alone can do the work in:

A and B together can complete a work in 3 days. They start together but after 2 days, B left the work. If the work is completed after two more days, A alona could do the work in