deepesh.gupta wrote: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 would have one more present to be wrapped, nine clerks would be required to guarantee that every present would be wrapped in one hour
Step 1 of the Kaplan Method for DS: Analyze the Stem
Q: Will all the presents be wrapped in within 1 hour? (yes/no)
We know that each clerk wraps between 20 and 30 (inclusive) presents per hour. We know there are 70 people in line.
We don't know how many clerks there are or how many presents each person has, so that's the information we need.
Step 2 of the Kaplan Method for DS: Evaluate the Statements
(1) we know there are at least 70 presents and exactly 6 clerks.
Well, 6 clerks will wrap between 120 and 180 presents in 1 hour, so it's possible that they'll get everything wrapped.
However, it's also possible that everyone in line has 1000 presents, so the wrapping might not be finished.
Maybe yes, maybe no: insufficient, eliminate A and D.
(2) 9 clerks guarantee that 180 presents get wrapped (20 minimum per clerk).
No information about the actual number of clerks, however: insufficient, eliminate B.
Combined:
Now that we have to, let's think about (2) some more.
The guarantee in (2) is based on each of the 70 patrons having 1 more present. So, the actual number of presents must be 180-70 = 110.
We now know that we have 6 clerks for 110 presents, guaranteeing that the work all gets done within an hour. Sufficient, choose C.
