While working alone at their constant rates computer x can process 240 files in 4 hours, and comp y 240 files in 8 hrs. if all files processed by these comp. are the same size how long would it take the two comp. working at the same time at their respective constant rates , to process a total of 240 files?
a. 2hrs
b. 2hrs 20 min
c. 2hrs 40 min
d. 6hrs
e. 6hrs 20 min

c) 2hrs 40 min

Explanation:

Rate of working of Computer X is = 240 files/ (4 × 60min)

= 1 file / min

Rate of working of Computer Y is = 240files/ (8×60min)

= 0.5 file/min

The combined rate for computer X & Y is = 1 + 0.5 = 1.5 file/ mins.

Therefore, time taken to process 240 files is = 240/1.5

= 160mins

= 2hrs 40mins

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