At a certain department store present-wrapping counter, each clerk will wrap no fewer than twenty and no more than thirty presents per hour. If seventy 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 clerks at the counter.
(2) If each person in line had one more present to be wrapped, nine clerks would be required to guarantee that every present would be wrapped in one hour.
IMO, (C) is the correct answer.
From the stem, we have the following meaningful information;
- There are 70 customers.
- One clerk will handle from 20 to 30 wrappings.
From Stat(1), we have the following meaningful information;
- There are 6 clerks.
From Stat(2), we have the following meaningful information;
- One customer has, on average, 2 gifts.
( let x be the average number of gifts. then, 9*20<70x+70<9*30.
2 is the only possible number of gifts)
From Stat(1), we don't know how many gifts are there, thus insufficient.
From Stat(2), we don't know how many clerks are there, thus insufficient.
From Stat(1)(2) combined, we know how many clerks & gifts are there, thus sufficient.
Auge um Auge, Zahn um Zahn !