in a certain commercial bank customers may withdraw cash through one of the two tellers at the counter on average one teller takes three minutes while the other teller takes five minutes to serve a customer if two tellers start to serve the customers at the same time find the shortest time it takes to serve 200 customers
1 helps 1/3 customer / min
2 helps 1/5 customer / min
so together 1/3+1/5 = (5+3)/15 =8/15 customers/min
t = 200 customers / 8/15 customers/min
= 200 * 15 / 8 min
= 375 min
which is about 6 1/4 hours
is equivalent to 6 hours and 15 minutes.
The formula for rate is:
Rate = Total output / Total input
In the case of this problem, the output is the total number of customers served, and the input is the total time taken to serve them. So the rate at which the two tellers can serve customers is:
Rate = Total customers served / Total time taken
Hope this helps!