Szechuan House offers chicken, shrimp, beef, vegetable, and tofu entrees served in either garlic sauce or green chili sauce. In how many ways can three entrees be served if no entree is served more than a total of once?
A)10
B)60
c)80
D)100
E)120
OAC
Szechuan House offers chicken, shrimp, beef,
This topic has expert replies
-
- Senior | Next Rank: 100 Posts
- Posts: 34
- Joined: Tue Oct 14, 2014 8:23 am
- Thanked: 1 times
- DavidG@VeritasPrep
- Legendary Member
- Posts: 2663
- Joined: Wed Jan 14, 2015 8:25 am
- Location: Boston, MA
- Thanked: 1153 times
- Followed by:128 members
- GMAT Score:770
First, we need to choose 3 entries from that list of 5, so we're looking for 5C3. (This is a combination, because order doesn't matter.) This gives us 5*4*3/3! = 10.
So there are 10 ways we can select our entrees.
Now, for each of the three entrees we eventually select, there are two options for sauce, so there are 2*2*2 = 8 ways we can select sauces for our three entrees.
There are 10 ways we can select our entrees, and 8 ways we can select our sauces to go with our entrees.
10*8 = 80
Answer is C
So there are 10 ways we can select our entrees.
Now, for each of the three entrees we eventually select, there are two options for sauce, so there are 2*2*2 = 8 ways we can select sauces for our three entrees.
There are 10 ways we can select our entrees, and 8 ways we can select our sauces to go with our entrees.
10*8 = 80
Answer is C
- GMATGuruNY
- GMAT Instructor
- Posts: 15539
- Joined: Tue May 25, 2010 12:04 pm
- Location: New York, NY
- Thanked: 13060 times
- Followed by:1906 members
- GMAT Score:790
Step 1: Choose 3 entreesgmat_winter wrote:Szechuan House offers chicken, shrimp, beef, vegetable, and tofu entrees served in either garlic sauce or green chili sauce. In how many ways can three entrees be served if no entree is served more than a total of once?
A)10
B)60
c)80
D)100
E)120
From the 5 entrees, the number of ways to choose the first entree = 5.
From the remaining 4 entrees, the number of ways to choose the second entree = 4.
From the remaining 3 entrees, the number of ways to choose the third entree = 3.
To combine these options, we multiply:
5*4*3 = 60.
Since the ORDER of the entrees does not matter -- CSB constitutes the same 3 entrees as SBC -- we divide by the number of ways the 3 entrees can be ARRANGED (3!):
60/3! = 10.
Step 2: Choose a sauce
Number of sauces that could be given to the first entree = 2. (garlic or chili)
Number of sauces that could be given to the second entree = 2. (garlic or chili)
Number of sauces that could be given to the third entree = 2. (garlic or chili)
To combine these options, we multiply:
2*2*2 = 8.
To combine our entree options with our sauce options, we multiply:
10*8 = 80.
The correct answer is C.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
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
Take the task of serving 3 entrees and break it into stages.gmat_winter wrote:Szechuan House offers chicken, shrimp, beef, vegetable, and tofu entrees served in either garlic sauce or green chili sauce. In how many ways can three entrees be served if no entree is served more than a total of once?
A)10
B)60
C)80
D)100
E)120
OAC
Stage 1: Choose 3 meal types
There are 5 meal types: chicken, shrimp, beef, vegetable, and tofu
Since the order in which we select 3 meal types does not matter, we can use COMBINATIONS
We can select 3 meals from 5 meals in 5C3 ways (= 10 ways).
So, we can complete stage 1 in 10 ways
If anyone is interested, we have a free video on calculating combinations (like 5C3) in your head: https://www.gmatprepnow.com/module/gmat-counting?id=789
Stage 2: Choose either garlic sauce or green chili sauce for the 1st selected meal.
We can complete this stage in 2 ways.
Stage 3: Choose either garlic sauce or green chili sauce for the 2nd selected meal.
We can complete this stage in 2 ways.
Stage 4: Choose either garlic sauce or green chili sauce for the 3rd selected meal.
We can complete this stage in 2 ways.
By the Fundamental Counting Principle (FCP), we can complete all 4 stages (and thus serve 3 entrees) in (10)(2)(2)(2) ways ([spoiler]= 80 ways[/spoiler])
Answer: C
--------------------------
Note: the FCP can be used to solve the MAJORITY of counting questions on the GMAT. For more information about the FCP, watch our free video: https://www.gmatprepnow.com/module/gmat-counting?id=775
Then you can try solving the following questions:
EASY
- https://www.beatthegmat.com/what-should- ... 67256.html
- https://www.beatthegmat.com/counting-pro ... 44302.html
- https://www.beatthegmat.com/picking-a-5- ... 73110.html
- https://www.beatthegmat.com/permutation- ... 57412.html
- https://www.beatthegmat.com/simple-one-t270061.html
- https://www.beatthegmat.com/mouse-pellets-t274303.html
MEDIUM
- https://www.beatthegmat.com/combinatoric ... 73194.html
- https://www.beatthegmat.com/arabian-hors ... 50703.html
- https://www.beatthegmat.com/sub-sets-pro ... 73337.html
- https://www.beatthegmat.com/combinatoric ... 73180.html
- https://www.beatthegmat.com/digits-numbers-t270127.html
- https://www.beatthegmat.com/doubt-on-sep ... 71047.html
- https://www.beatthegmat.com/combinatoric ... 67079.html
DIFFICULT
- https://www.beatthegmat.com/wonderful-p- ... 71001.html
- https://www.beatthegmat.com/ps-counting-t273659.html
- https://www.beatthegmat.com/permutation- ... 73915.html
- https://www.beatthegmat.com/please-solve ... 71499.html
- https://www.beatthegmat.com/no-two-ladie ... 75661.html
- https://www.beatthegmat.com/laniera-s-co ... 15764.html
Cheers,
Brent
GMAT/MBA Expert
- Jeff@TargetTestPrep
- GMAT Instructor
- Posts: 1462
- Joined: Thu Apr 09, 2015 9:34 am
- Location: New York, NY
- Thanked: 39 times
- Followed by:22 members
Solution:gmat_winter wrote:Szechuan House offers chicken, shrimp, beef, vegetable, and tofu entrees served in either garlic sauce or green chili sauce. In how many ways can three entrees be served if no entree is served more than a total of once?
A)10
B)60
c)80
D)100
E)120
OAC
This is a combination question testing us on the fundamental counting principle. The first step is to determine the number of ways in which we can select 3 dishes. We are selecting 3 dishes from 5 so we have 5C3, which is calculated as follows:
5C3 = 5!/[(5-3)! x 3!] = 5!/2! x 3! = (5x4x3x2x1)/(2x1x3x2x1) = 120/12 = 10
If you don't know how to use the combination formula, here is a method that will work equally well.
We are choosing 3 entrées from a pool of 5 possible entrées. That is, there are 3 decisions being made:
Decision 1: Choosing the first entrée
Decision 2: Choosing the second entrée
Decision 3: Choosing the third entrée
Five different entrées are available to be the first selection.
For the second selection, 4 remaining entrées are available because 1 entrée was already chosen.
For the third selection, 3 remaining entrées are available remain because 2 entrées have already been selected.
The product of these options will represent the numerator of our calculation, so we will have: 5 x 4 x 3 = 60
The final step is to divide by the factorial of the number of "decisions." In this case, we had 3 decisions so we divide by divide by 3!.
(5x4x3)/3! = (5x4x3)/(3x2x1) = 60/6 = 10
We see that there are 10 ways to choose 3 entrées from 5 available entrées. That is, there are ten 3-entrée combos. For each entrée in any of these 3-entrée combos, there are two selections of the sauces. That is, if entrée one, entrée two and entrée three are in the 3-entrée combo, we can serve each with either garlic sauce or green chili sauce. Therefore, for each 3-entrée combo, there are a total of 2 x 2 x 2 = 8 ways to serve them with a sauce.
If this is difficult to see, let's say a 3-entrée combo consists of chicken (C), shrimp (S) and beef (B) and let's let g be garlic sauce and c be green chili sauce. We will have:
1) C-g, S-g, B-g
2) C-g, S-g, B-c
3) C-g, S-c, B-g
4) C-g, S-c, B-c
5) C-c, S-g, B-g
6) C-c, S-g, B-c
7) C-c, S-c, B-g
8) C-c, S-c, B-c
Finally, since there are ten 3-entrée combos and each combo has 8 selections, there are a total of 10 x 8 = 80 ways to pick three entrées (each with a sauce) where no entrée is served more than once.
The answer C
Jeffrey Miller
Head of GMAT Instruction
[email protected]
See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews