# General Maths 2015 HSC error? (1 Viewer)

#### sourmilk

##### Active Member
http://www.boardofstudies.nsw.edu.au/hsc_exams/2015/exams/2015-hsc-maths-general-2.pdf

A Student Representative Council (SRC) consists of five members. Three of the members
are being selected to attend a conference.
In how many ways can the three members be selected?
(A) 10
(B) 20
(C) 30
(D) 60

Isn't the answer D? Apparently in the answers the answer is A. Both me and my friend got D and we don't know how it's A, and I literally wrote all the possible combinations and it's definitely more than 10.

#### davidgoes4wce

##### Well-Known Member
I went through that question today , and I thought the answer was A.

$\bg_white ^{5}C_3=10$

It doesn't matter about the 'order' of the selections. (*Unordered selection)

#### sourmilk

##### Active Member
I went through that question today , and I thought the answer was A.

$\bg_white ^{5}C_3=10$

It doesn't matter about the 'order' of the selections. (*Unordered selection)
OoooooooooOOh thank you so much! my friend told me to dismiss that it was wrong ahahahaha

#### Mongoose528

##### Member
For combinations without repetition, the formula is n!/r!(n-r)!

Where n is the number of things to choose from and r is the amount of things we chose

So in this question, there are 5 people to choose from and we have to choose 3 of them

So the amount of ways is 5!/(3!(5-3)!) = 5!/(3!2!) = 120/(6*2) = 120/12 = 10

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