Question : The average height of 30 boys out of a class of 50 is 160 cm. If the average height of the remaining boys is 165 cm, the average height of the whole class (in cm) is:

Question : What is the third proportion of $2 \sqrt{3}$ and $6 \sqrt{5}$?

Question : Anil completed a certain journey by car. If he covered 35% of the distance at 70 km/h, 40% of the distance at 80 km/h and the remaining distance at 50 km/h, his average speed (in km/h) for the entire journey is:

Question : A motorist travels to a place 150 km away at an average speed of 50 km/h and returns at 30 km/h. His average speed for the whole journey in km/h is

Question : A bus travels for three hours at 60 km/hr, four hours at 50 km/hr, and the next five hours at 50 km/hr. Find its average speed.