To furnish a room in a model home, an interior decorator is to select 2 chairs and 2 tables from a collection of chairs and tables in a warehouse that are all different from each other. If there are 5 chairs and 150 different combinations are possible, how many tables are in the warehouse?
6
8
10
15
30
OA 6
Model home furniture
This topic has expert replies
GMAT/MBA Expert
- Brent@GMATPrepNow
- GMAT Instructor
- Posts: 16207
- Joined: Mon Dec 08, 2008 6:26 pm
- Location: Vancouver, BC
- Thanked: 5254 times
- Followed by:1268 members
- GMAT Score:770
Total # of combinations = (# of ways to select 2 chairs)(# of ways to select 2 tables)josh80 wrote:To furnish a room in a model home, an interior decorator is to select 2 chairs and 2 tables from a collection of chairs and tables in a warehouse that are all different from each other. If there are 5 chairs and 150 different combinations are possible, how many tables are in the warehouse?
A) 6
B) 8
C) 10
D) 15
E) 30
OA 6
So, 150 = (# of ways to select 2 chairs)(# of ways to select 2 tables)
# of ways to select 2 chairs
5 tables, choose 2 of them.
Since the order of the selected chairs does not matter, we can use combinations.
This can be accomplished in 5C2 ways (10 ways)
Total # of combinations = (# of ways to select 2 chairs)(# of ways to select 2 tables)
150 = (10)(# of ways to select 2 tables)
(# of ways to select 2 tables) = 15
# of ways to select 2 tables
Let N = # of tables.
We have N tables, choose 2.
This can be accomplished in NC2 ways
So, NC2 = 15
Our goal is to find the value of N.
From here, we can just start checking answer choices.
We get 6C2 = 15, so N = 6, which means there are 6 tables.
Answer = A
If anyone is interested, we have a free video on calculating combinations (like 6C2) in your head: https://www.gmatprepnow.com/module/gmat-counting?id=789
Cheers,
Brent