permutations question

Expert replies

saigopal7: Newbie | Next Rank: 10 Posts; Posts: 1; Joined: Sat Aug 19, 2006 3:34 am

by saigopal7 » Fri Dec 01, 2006 7:46 pm

Pat's pizza offers thick,thin, or deep-dish style crust.There are 8 choices for toppings.

In how many ways can u choose a pizza with three different toppings?

Ans:1008

Like this post

Source: Beat The GMAT — Problem Solving | Fri Dec 01, 2006 7:46 pm

800guy: Master | Next Rank: 500 Posts; Posts: 354; Joined: Tue Jun 27, 2006 9:20 pmFollowed by: 5 members; Thanked: 11 times

by 800guy » Sat Dec 02, 2006 11:46 am

this is a permutations problem

number of permutations for ONE pizza:
8P3 =

8! divided by (8 - 3)! = 336

multiply this by 3 since there are 3 types of crust

336 x 3 = 1008

hope this helps!!

Like this post

projase: Junior | Next Rank: 30 Posts; Posts: 14; Joined: Sun Dec 03, 2006 2:45 pm

Why is this a permutation problem?

by projase » Tue Dec 05, 2006 3:06 pm

Why is this a permutation and not a combination problem?

For me the solution is 3x 8C3.....

800guy wrote:this is a permutations problem

number of permutations for ONE pizza:
8P3 =

8! divided by (8 - 3)! = 336

multiply this by 3 since there are 3 types of crust

336 x 3 = 1008

hope this helps!!

Like this post

800guy: Master | Next Rank: 500 Posts; Posts: 354; Joined: Tue Jun 27, 2006 9:20 pmFollowed by: 5 members; Thanked: 11 times

by 800guy » Tue Dec 05, 2006 3:15 pm

you're right projase

i think this should be a combinations problem after all. somehow i got the right answer though using the permutations equation

Like this post

one_pacifist: Newbie | Next Rank: 10 Posts; Posts: 3; Joined: Mon Nov 22, 2010 12:34 am; Location: India

by one_pacifist » Thu Feb 03, 2011 8:11 pm

hi all

new to permutations and combinations topic, so need help on this ....

q) A set of 6 questions contains true /false type questions.
Maximum how many students can take the test if all the students answer differently from others and must attempt all the questions ?

a gud explanation on answer will help a lot!!!!!!

Be Vulnerable

Like this post

Night reader: Legendary Member; Posts: 1337; Joined: Sat Dec 27, 2008 6:29 pmFollowed by: 10 members; Thanked: 127 times

by Night reader » Thu Feb 03, 2011 10:13 pm

saigopal7 wrote:Pat's pizza offers thick,thin, or deep-dish style crust.There are 8 choices for toppings.

In how many ways can u choose a pizza with three different toppings?

Ans:1008

8P3 * 3!=8!/(8-3)! *3=1008

call pizzas: thick-x,thin-y, deep-dish-z

x, y or z can be chosen in 8 ways as the first order
x, y or z can be chosen in 7 ways
x, y or z can be chosen in 6 ways
(8*7*6) *3=1008

Last edited by Night reader on Sat Feb 05, 2011 1:12 am, edited 1 time in total.

Like this post

rohu27: Legendary Member; Posts: 586; Joined: Tue Jan 19, 2010 4:38 amFollowed by: 5 members; Thanked: 31 times; GMAT Score:730

by rohu27 » Fri Feb 04, 2011 9:41 pm

Nightreader,

Please clarify this one.
we are asked to choose a single pizza wth 3 diff toppings.
no. of ways to choose 3 toppings out of 8 is 8c3.
as the no. of crusts are 3, total combnations are: 3*8c3=168 combinations.

or is it tht we need to consider a thin crust pizza wth ABC toppings diff frm a thin crust pizza wth BAC toppgs?

Totally confused

Night reader wrote:
saigopal7 wrote:Pat's pizza offers thick,thin, or deep-dish style crust.There are 8 choices for toppings.

In how many ways can u choose a pizza with three different toppings?

Ans:1008
8P3 * 3!=8!/(8-3)! *3!=2116 this should be the correct answer in reality

or call pizzas: thick-x,thin-y, deep-dish-z

x, y or z can be chosen in 8 ways as the first order
x, y or z can be chosen in 7 ways
x, y or z can be chosen in 6 ways
(8*7*6) *3!=2116

Like this post

Night reader: Legendary Member; Posts: 1337; Joined: Sat Dec 27, 2008 6:29 pmFollowed by: 10 members; Thanked: 127 times

by Night reader » Sat Feb 05, 2011 1:11 am

I've edited the previous solution; the problem doesn't explicitly state the topping order, so I assumed that ABC is different from BAC

if the topping order doesn't matter than 3*6C3 if it does matter then 3*6P3

rohu27 wrote:Nightreader,

Please clarify this one.
we are asked to choose a single pizza wth 3 diff toppings.
no. of ways to choose 3 toppings out of 8 is 8c3.
as the no. of crusts are 3, total combnations are: 3*8c3=168 combinations.

or is it tht we need to consider a thin crust pizza wth ABC toppings diff frm a thin crust pizza wth BAC toppgs?

Totally confused

Night reader wrote:
saigopal7 wrote:Pat's pizza offers thick,thin, or deep-dish style crust.There are 8 choices for toppings.

In how many ways can u choose a pizza with three different toppings?

Ans:1008
8P3 * 3!=8!/(8-3)! *3!=2116 this should be the correct answer in reality

or call pizzas: thick-x,thin-y, deep-dish-z

x, y or z can be chosen in 8 ways as the first order
x, y or z can be chosen in 7 ways
x, y or z can be chosen in 6 ways
(8*7*6) *3!=2116

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

559 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (560 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review