AAPL wrote:GMAT Prep
Of the 20 people who each purchased 2 tickets to a concert, some used both tickets, some used only 1 ticket, and some used neither ticket. What percent of the tickets that were purchased by the 20 people were used by those people?
1) Of the 20 people, 10 used only 1 ticket.
2) Of the 20 people, 4 used neither ticket.
OA C
Here's one approach:
Target question: What percent of the tickets that were purchased by the 20 people were used by those people?
Given: 20 PAIRS of tickets were bought by 20 PEOPLE. Some people used both tickets, some used only 1 ticket, and some used 0 tickets
So, we have the following table to represent what happened with each of the 20 PEOPLE
To answer the
target question, we need to know the number of people in each of the two HIGHLIGHTED boxes.
Statement 1: Of the 20 people, 10 used only 1 ticket.
So, we know that there are 10 people in the middle box, but we don't know about the other two boxes. This leaves several possible cases. Here are two:
In the
top case, we see that 10 of the 40 tickets were used by the purchaser. So,
25% of the tickets were used by the purchaser.
In the
bottom case, we see that 30 of the 40 tickets were used by the purchaser. So,
75% of the tickets were used by the purchaser.
Since we cannot answer the
target question with certainty, statement 1 is NOT SUFFICIENT
Statement 2: Of the 20 people, 4 used neither ticket.
So, we know that there are 4 people in the right-hand box, but we don't know about the other two boxes. This leaves several possible cases. Here are two:
In the
top case, we see that 32 of the 40 tickets were used by the purchaser. So,
80% of the tickets were used by the purchaser.
In the
bottom case, we see that 16 of the 40 tickets were used by the purchaser. So,
40% of the tickets were used by the purchaser.
Since we cannot answer the
target question with certainty, statement 2 is NOT SUFFICIENT
Statements 1 and 2 combined
When COMBINED the statements give us
one and only one possible case:
In this case, we see that 22 of the 40 tickets were used by the purchaser. So,
55% of the tickets were used by the purchaser.
Since we can answer the
target question with certainty, the combined statements are SUFFICIENT
Answer = C
Cheers,
Brent
