College algebra work

Question

One computer can do a job twice as fast as another. Working together both computers can do a job in 2 hours. How long would it take each computer working alone to do the job.

Answer 1

Let x = the number of hours in which the faster computer could do the job and 2x the number of hours for the slower one

 

(1/x) + (1/2x) = 1/2

(2/2x) + (1/2x) = 1/2

(3/2x) = 1/2

2x = 6 and x =3

Explaining why this works is always difficult for me, but it begins with recognizing that (1/x) is a rate.

If you need further assistance, please send me a message & I will try to explain further.