A room is to be painted by Jane and Sally working together. How long w

This equation comes in handy....again

\(W=\frac{AB}{A+B}\) where A and B are rates and W is the work done.

Statement 1: Gives A, nothing about B. Not sufficient
Statement 2: Gives B, nothing about A. Not sufficient

Combined: Sufficient. Answer is C

A problem like this should take no more than 30 seconds.

A room is to be painted by Jane and Sally working together. How long will it take them to paint the room together?

1. Jane can paint the room in 16 hours, working alone.

As we want to find the work done by both of them together, having information on just one persons work will not be sufficient.

In this case we only Jane's time taken to complete the work but not Sally's

Hence (1) =====> is NOT SUFFICIENT

2. Sally can paint the room in 12 hours, working alone.

Once again, as we want to find the work done by both of them together, having information on just one persons work will not be sufficient.

In this case we only know Sally's time taken to complete the work but not Jane's.

Hence (2) =====> is NOT SUFFICIENT

Now, lets combine (1) and (2)

As you might know that, in order to find out time taken for both of them working together can be calculated by the formula

\(Work Done (Together) = \frac{a * b}{a + b}\)

Note, we need not actually solve the problem here, even knowing that we can get an answer should be sufficient.


Hence, Answer is C

Just to add

Combined Rate =AB/A+B)
Combined time=(A+B)/AB

This formula can only be used if individual time is given.