Two computers working together can finish a search in 30 seconds. one of these computers can finish in 50 seconds. how long would it take the second computer to finish the same search if it were working alone?

I think the answer is 10 seconds, because 50+10=60/2=30. I'm not sure if that's right tho

The best way to look at it is assume there are 60 units of work and the two computers together complete the task in 30 seconds. So together they can do 2 units per second on average. The first computer can do the 60 units of work by itself in 50 seconds, which is 60/50 so it's doing most of the work in the group since the average of the individuals in the group is lower.

270 books in each shelves