A soap factory makes 600 units in 9 days with help of 20 machines .how many units can be made in 12 days with the help of 18 machines?

A) 680

B) 720 ✓

C) 760

D) 810

Explanation:

20=k×600×91​.
This gives the constant of proportionality
k=60020×9​
Let $x$ be the number of units which can be manufactured using $18$ machines in $12$ days. Using the same reasoning, we obtain
18=k×x×121​.
Thus we obtain
x=k18×12​=20×918×12×600​=720.
Hence $720$ units can be manufactured using $18$ machines for $12$ days.