Question 12
An, Bình and Châu work together on a landscape painting for their art homework. Working alone, they would finish it in 9, 10 and 12 hours respectively. An and Bình first paint together for 3 hours, then An stops. Bình and Châu finish the painting. How much time does the whole job take?
Model clarification: each person works at a constant rate, and their rates add when they work together.
Model clarification: each person works at a constant rate, and their rates add when they work together.