Question

Working alone at their respective constant rates, machine A and machine B can fill a certain order in 3 hours and 6 hours, respectively. If the two machines work simultaneously at their respective constant rates, how many hours does it take the two machines to fill?

Answer 1

Answer: 2 hours

Step-by-step explanation:

Given : Working alone at their respective constant rates, machine A and machine B can fill a certain order in 3 hours and 6 hours, respectively.

Let t be the time taken by both of them working together.

Then, according to the question, we have

$\dfrac{1}{t}=\dfrac{1}{3}+\dfrac{1}{6}\\\\\Rightarrow\dfrac{1}{t}=\dfrac{2+1}{6}\ \ [\because\ L.C.M. (3,6)=6]\\\\\Rightarrow\dfrac{1}{t}=\dfrac{3}{6}=\dfrac{1}{2}\\\\\Rightarrow t=2$

Hence, it will take 2 hours by the two machines .