## anonymous one year ago How many groups of four shirts can you choose from six shirts? Determine if the word problem is a permutation or a combination, then evaluate. Which question below is a permutation? How many different teams of four runners can a coach choose from a group of seven runners? You and three friends want to line up next to one another for a picture. How many ways can the picture be taken? You want to choose three pairs of shorts from five to go on vacation. How many groups of three pairs of shorts can you choose? How many groups of five movies can be chosen from 11?

1. anonymous

@isaac4321

2. welshfella

combinations of 4 from 6 = 6C2

3. anonymous

?

4. welshfella

have you seen that notation before 6C2?

5. welshfella

6. welshfella

6C2 is equivalent to 6C4

7. anonymous

$_{n}C _{r} = \frac{ n! }{ r!\left( n-r \right)! }$$_{6}C _{2} = \frac{ 6! }{ 2!\left( 4! \right) }$

8. anonymous

its asking for a number not a 6C2 lol im confused

9. welshfella

yes osprey has the formula a short way of working it out is 6*5 --- 2*1

10. welshfella

- starting with 6 then going down to 5 because of the 2 6C4 = 6*5*4*3 ------ 4*3*2*1 which works out to the same value

11. welshfella

6C2 means the number of combinations of 2 from 6

12. welshfella

so for the first part its 6*5 / 2*1 = 15

13. anonymous

ohhh

14. anonymous

thank you

15. welshfella

yw The difference between combinations and permutations is that the order does not matter in combinations. The groups of 4 shirts can be in any order.

16. welshfella

Now for the second part there is one in which the order matters which do you think it is?

17. anonymous

is d correct for 2

18. welshfella

No - in which one do you have a different result if there is a different arrangement?

19. welshfella

Hint: Click

20. anonymous

b

21. welshfella

lol yes

22. welshfella

different arrangement - different picture

23. anonymous

thanx

24. welshfella

get it now? i think you do yw