First, let's make an equation out of the first sentence in the problem statement. When four of each computers are used, they can finish a task in 11 minutes together. The question is, how fast is the rate of each computer? We let that rate be x which is in units of hours per unit computer. So, the first equation would be:
4x = 11
Solving for x,
x = 2.75 minutes
That means that each of the four computers has an individual rate of 2.75 minutes. Now, for the succeeding sentence, we replace two of the computers with a much faster time. That means it would take a shorter time by 20%. The new time would then be:
New time = 2.75 ( 1 - 0.2) = 2.2 minutes
Therefore, the total amount of time for the task to be done by 2 original and 2 new computers is
Total time = 2(2.75) + 2(2.2)
Total time = 9.9 minutes
