GMAT Practice Question: A technology startup will select 1 project manager from 9 candidates, 2...
Question
A technology startup will select 1 project manager from 9 candidates, 2 software engineers from 7 candidates, and 1 designer from 20 candidates to form a core team of 4 professionals. If no candidate is eligible for more than one role, how many different teams are possible?
- 3,360
- 3,500
- 3,762
- 3,780
- 3,920
Topics: combinations, p&c multisource
Solution
Step 1
We first calculate the number of ways to choose one project manager from nine eligible candidates.
C(9,1) = \frac{9!}{1!8!} = \frac{9\times8\times7\times6\times5\times4\times3\times2\times1}{1\times(8\times7\times6\times5\times4\times3\times2\times1)} = 9
Step 2
We then calculate the number of ways to choose two software engineers from seven eligible candidates, where the two positions are identical.
C(7,2) = \frac{7!}{2!5!} = \frac{7\times6\times5\times4\times3\times2\times1}{(2\times1)\times(5\times4\times3\times2\times1)} = \frac{7\times6\times5\times4\times3\times2\times1}{(2\times1)\times(5\times4\times3\times2\times1)} = 21
Step 3
Next, we calculate the number of ways to choose one designer from twenty eligible candidates.
C(20,1) = \frac{20!}{1!19!} = \frac{20\times19\times18\times17\times16\times15\times14\times13\times12\times11\times10\times9\times8\times7\times6\times5\times4\times3\times2\times1}{1\times(19\times18\times17\times16\times15\times14\times13\times12\times11\times10\times9\times8\times7\times6\times5\times4\times3\times2\times1)} = 20
Step 4
Because the project manager selection, the software engineer selection, and the designer selection are all independent, we multiply these counts to find the total number of teams.
9 \times 21 \times 20 = 3{,}780
Answer
D
