Hasan can paint 54 walls in 27 minutes. Rafiq can paint 25 walls in 10 minutes. Working together, how many walls can they paint in 20 minutes?

Question: Hasan can paint 54 walls in 27 minutes. Rafiq can paint 25 walls in 10 minutes. Working together, how many walls can they paint in 20 minutes?

Solution:
Hasan can paint in 1 minute = 54 ÷ 27 = 2 walls

Rafiq can paint in 1 minute = 25 ÷ 10 = 25/10 = 5/2 walls

∴ Together they can paint in 1 minute = 2 + (5/2) walls
= (4 + 5)/2 = 9/2 walls

∴ In 20 minutes, they can paint = (9/2) × 20 walls
= (9 × 20)/2
= 90 walls