UPSC Civil Services 2020 Prelims General Studies Paper II

A car travels from a place X to place Y at an average speed of vkm∕hr, from Y to X at an average speed of 2v‌‌km∕hr, again from X to Y at an average speed of 3v‌‌km∕hr and again from Y to X at an average speed of 4v‌‌km∕hr. Then the average speed of the car for the entire journey