each of two computers can process bills at 160/min a newer model can process bills at 200/min after the first two computers have worked 1.5 min they are joined by the third computer how long will it take from the time the first two computers are turned on to process 1780?

Based on the rate at which all three computers process bills, the time taken for the computers to process 1,780 bills is 4 minutes.

First find the number of bills left when the third computer joined:

= 1,780 - (160 x 1.5 mins) - (160 x 1.5 mins)

= 1,300

Then the average speed of all three computers is:

= 160 + 160 + 200

= 520 bills per minute

The time taken to finish up the other bills would be:

= 1,300 / 520

= 2.5 minutes

Add this to the minutes already elapsed before the third computer was used:

= 2.5 + 1.5

= 4 minutes

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