It takes 21 minutes for 5 people to paint 7 walls. how many minutes does it take 3 people to paint 5 walls. .

It would take 15 minutes.
21/7=3
5/3=1.666666666667
1.6666666667*3=approx. 5
5*3=15 
Hope it hepls :)

It would take 15 minutes.
21/7=3
5/3=1.666666666667
1.6666666667*3= 5
5*3=15 

So if you do 21 divied by 7 that equals 3. then you do 5 divied by 3=1.666666666667 you divide the 3 bc that's the answer you got for 21/7. then you do 1.666666666667 x3. bc you had that answer for the last problem. then you just have 2 multiply 5x3 and that equals 15.