Question 25940: pls.help me with this. a bank teller counts a certain amount of money in 20 mins, but if she is helped by another teller, they count the money in 15 mins. how long would it take the second teller to count the money alone?
Found 2 solutions by Earlsdon, wuwei96815:
Answer by Earlsdon(6294)   (Show Source):
You can put this solution on YOUR website! Here's one approach: Let the tellers be Teller A and Teller B.
If A can do the job in 20 minutes, then he/she can do 1/20 of the job in 1 minute.
If A and B together can do the job in 15 minutes, then they can do 1/15 of the job in 1 minute.
So, if we subtract A's part of the job for 1 minute from the part of the job for 1 minute for A + B, then we will have the part of the job done by B in 1 minute.
A + B = 1/15
B = 1/15-A But A = 1/20, so:
B = 1/15 - 1/20
B = 4/60 - 3/60
B = 1/60 which means that Teller B can do 1/60 of the job in 1 minute, therefore, B can do the entire job in 60 minutes.
Answer: It would take Teller B 60 minutes to count the money.
Answer by wuwei96815(245) (Show Source):
You can put this solution on YOUR website! If doubling the work force to two tellers does not reduce the work time by half or more, then we must assume that the second teller is slower than the first teller. The question is how much slower?
15 minutes/20 minutes = 0.75 = 75%
So, working together the two tellers were (100% - 75%) or 25% faster than the first teller working alone?
If we assume that the second teller is responsible for the 25% increase, then we can assume that working alone the second teller will take 25% more time than the first teller or 20 + 25%(20) = 25 minutes.
So, logic tells us that the second teller will take 25 minutes working alone.
I hope that is right.
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