Bunuel
Take the task of distributing the 5 books and break it into
stages.
Let's let A, B, C, D, and E represent the 5 books
Stage 1: Select a person to receive book A
There are 10 people to choose from, so we can complete stage 1 in
10 ways
Stage 2: Select a person to receive book B
Since no person can receive more than 1 book, there are 9 people who can receive book B
So we can complete stage 2 in
9 ways
Stage 3: Select a person to receive book C
8 people remaining. So we can complete stage 3 in
8 ways
Following the pattern, we can complete stage 4 (selecting a person to receive book D) in
7 ways
And we can complete stage 5 (selecting a person to receive book E) in
6 ways
By the Fundamental Counting Principle (FCP), we can complete all 5 stages (and thus distribute all 5 books) in
(10)(9)(8)(7)(6) ways
Check the answer choices.....
Notice that D) \(10C5 \times 5!= \frac{10 \times 9 \times 8 \times 7 \times 6}{5 \times 4 \times 3 \times 2 \times 1} \times 5! \)
\(= \frac{10 \times 9 \times 8 \times 7 \times 6}{5 \times 4 \times 3 \times 2 \times 1} \times 5 \times 4 \times 3 \times 2 \times 1 \)
\(= 10 \times 9 \times 8 \times 7 \times 6 \)Answer: D
Note: the FCP can be used to solve the MAJORITY of counting questions on the GMAT. So, be sure to learn it.
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