Question

To complete a tank, A and C three noses take 20 minutes to 15 minutes and 12 minutes respectively, so how long does it take to open the three nulls together.

Answer 1

step 1: find what part of tank they can fill in one min.

step 2: add the above results.

step 3: reciprocate it

step 4: you have almost reached the ans. use commeon sense for the last step