12 marbles are selected at random form a large collection of white , red, green and yellow marbles . The number of marbles of each color is unlimited. Find the probability that the selection contains at least one marble of each color ?

a motor -cycle covers 40 Km with a speed of 20 km /hr. Find the speed of the motor -cycle for the next 40 km j...

A man can row 6 km / hr in still water. It the speed of the current is 2 km / hr , it takes 3 hrs more in upst...

The respective ratio between the speed of a car , a train , and a bus is 5 : 9 : 4 . The average speed of the...

Three angles of a triangle are in proportion 5: 6: 7. Then what is the difference in degrees between he bigges...

A water tank has two taps ( Tap-1 and Tap-2) : Tap-1 can fill a tank in 8 hours and Tap-2 can empty the tank i...

The average of the three numbers x , y and z is 45 , x is greater than the average of y and z by 9. The averag...