A motorist travels to a place 150 km away at an average speed of 50 km per hour and returns at 30 km per hour. His average speed for the whole journey in km per hour is:
In a certain college the number of girls is twice the number of boys. 1/5th of the girls and 1/8th of the boys took part in a social camp. What part of the total number of students took part in the camp ?