If one typist can type a certain manuscript in 8 minutes,

Since 2 people working together is a common problem, it's better to remember that if A and B take time a and b to do the same work, they both together would do the same work in ab/(a+b), If C joins them, (ab+bc+ca)/(a+b+c).

Pawargmat, indeed, yr formula is very handy!!
Alex.

I would do this problem without computation.

If one typist can type a certain manuscript in 8 minutes, while another typist can type the same manuscript in 12 minutes, how long would it take both typists, working simultaneously, to type the manuscript?

We know that two identical typists that could do it in 8 minutes independently could do it in 4 minutes together.

We know that two identical typists that could do it in 12 minutes independently could do it in 6 minutes together.

The answer must be between 4 and 6.

Futhermore, since the fast typist will do more of the work, the time spent will be quicker than the mean of those two numbers (5).

B is the only choice between 4 and 5 minutes.

I have repeatedly displayed my foibles throughout this forum and realize that I have no position to make judgments-- but this is a problem that many of us should be able to do in fewer than ten seconds.

Ha Ha. While I agree with the answer for the purposes of the GMAT, I would like to point out that this is one of those problems with a math solution that doesn't make sense in the physical world. Let's say the manuscript was one page (both these typist are kinda slow). The answer assumes that both typist are working simultaneously. I would like to see a typewritter that allows two typists to work on the same page simultaneously. Typing a manuscript is also a "forward facing" process. Where does the second person start? (Ideally, the second person would start at the end at work backward, but I have seen to many typist adept at that either <Grin>).

Just some food for thought...

yeah... hardly can two persons type simultaneously...
maybe they change one another after each word?