Quantidude

Two men A and B can complete a work in 18 and 12 hours respectively.Both the men start working together at 7 a.m. and complete the work at 3 p.m. Find the minimum possible time for which either of the two men did not work during that period?

Average marks of 30 boys is 30. New group of x boys whose avg marks is y are added to the group .Sum of x and y is 40.what can be the max average score of the new group?

Try solving without pen paper!

A man runs the first lap of race at 30 km/hr.At what speed he must run the second lap so that his average speed for 2 laps is 60 km/hr?

Time: 2 sec