Why wasn't cross multiplication used.

Five editors finish a project in 3 1/2 weeks. How many editors are needed to complete the same project in 1 1/6 weeks

5/3.5= x/1.16

1 answer

It would work if you had used the correct number

1 1/6 weeks is NOT 1.16 it is 7/6 , so

secondly, this is not a direct proportion, but rather an inverse proportion.
That is, the more workers you have, the less time it takes.

the correct proportion is
5/x = (7/6) / 3.5

then (7/6)x = 3.5(5)
x = 17.5(6/7) = 15