At a certain department store present-wrapping counter, each clerk will wrap no fewer than 20 and no more than 30 presents per hour. If 70 people are standing in line, will all of their presents be wrapped after one hour?
1. Each person in line has at least one present to be wrapped by one of the six clearks at the counter.
2. If each person in line had one more present to be wrapped, 9 clerks would be required to guarantee that every present would be wrapped in one hour.
What is the answer?
Answer is C.
We have to consider the "minimum" number of presents that will be wrapped in an hour..
A ...says the minimum # of presents are 70...thats no good ...we need the total # of presents
B... If 9 clerks are required to "guarantee" ... then the total number of presents are 9 * 20 = 180 ( minimum rate of wrapping is 20 per hour)
But this is the case where each person in line has ONE MORE present in hand...so the actual # of presents is 180 - 70 =110
But we dont know the existing # of clerks..so insufficient
Combine...we now know existing # of clerks is 6 ..and they can wrap a minimum of 120 presents in an hour...so yes, all the presents will be wrapped in an hour.