Direct or inverse proportion

Question

It takes 2 people to bake 7 cakes in just 5 hours. 11 people baked 17 cakes. How long did it take them?

Answer 1

7 cakes take 10 man-hours

 

7 : 10 :: 17 : h       proportion

7h = (10)(17)        product means/extremes

h = 170/7 

 

17 cakes need 170/7 man-hours

17 cakes need 2.2 hours for 11 men to bake      (170/77)