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It takes 32 minutes for 3 people to paint 4 walls.

How many minutes does it take 4 people to paint 7 walls?

It will take 8 minutes for 3 people to paint 1 wall.....then each person paints 1/24 of a wall in1 minute

Then 4 people will paint 4(1/24)  =  1/6 of a wall in one minute

So  4 people will take.....7 / (1/6)   =  42 minutes to paint 7 walls

It takes 32 minutes for 3 people to paint 4 walls.

How many minutes does it take 4 people to paint 7 walls?

7:4 walls =4:3 people=M:32 minutes. Therefore:
M = (7/4)  / (4/3) x 32
M = 42 minutes required for 4 people to paint 7 walls.