A car travels 180 km from A to B at 60 kilometers per hour and returns from B to A along the same route at 90 kilometers per hour. The average speed, in kilometers per hour, for the round trip is :

A man has 72 green marbles and 108 red marbles. He decides to pack them into packets of the same size, each co...

A boat sails m miles upstream at the rate of r miles per hour. If the rate of the stream is s miles per hour,...

A wheel rotates 10 times per minute and moves 20 feet during each rotation. How many feet does the wheel move...

3x-1#2x is true for all values of x EXCEPT

A petrol tank that is 1/2 full has 8 gallons petrol removed. The tank is then 1/10 full. What is the capacity,...

If x : y = 2 : 3, and m : n= 9 : 4, find the ratio xn : ym.