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# Statistics as level cie math question ; urgent watch

1. Fahad has 4 different coloured pairs of shoes (white, red, blue and black), 3 different coloured pairs of jeans (blue, black and brown) and 7 different coloured tee shirts (red, orange, yellow, blue, green, white and purple).

(i) Fahad chooses an outfit consisting of one pair of shoes, one pair of jeans and one tee shirt. How many different outfits can he choose? [1]
this question confuses me although it just has one mark , so it is supposed to be really simple .
The answer in the markscheme is 7x3x4=84
But my question is why ? And why can't I use combination for eg 7C1+4C1+3C1=14
Please do explain to me why . Any help would be great.
2. (Original post by Sammysammy99)
Fahad has 4 different coloured pairs of shoes (white, red, blue and black), 3 different coloured pairs of jeans (blue, black and brown) and 7 different coloured tee shirts (red, orange, yellow, blue, green, white and purple).

(i) Fahad chooses an outfit consisting of one pair of shoes, one pair of jeans and one tee shirt. How many different outfits can he choose? [1] this question confuses me although it just has one mark , so it is supposed to be really simple .
The answer in the markscheme is 7x3x4=84
But my question is why ? And why can't I use combination for eg 7C1+4C1+3C1=14
Please do explain to me why . Any help would be great.
First off 7x3x4 is the same as 7C1 x 3C1 x 4C1, and you could do it via combinations.

So, why multply rather than add?

Because for each choice of one item, you could have any of the other items.

E.g. for one particular choice of shoes and jeans you could have any of the 7 tee shirts.
For another choice, again you could any of the 7
How many combinations of shoes and jeans are there? 4 x 3, and for each of those combinations you could have any of the 7 tee shirts, so 4x3x7.
3. (Original post by ghostwalker)
First off 7x3x4 is the same as 7C1 x 3C1 x 4C1, and you could do it via combinations.

So, why multply rather than add?

Because for each choice of one item, you could have any of the other items.

E.g. for one particular choice of shoes and jeans you could have any of the 7 tee shirts.
For another choice, again you could any of the 7
How many combinations of shoes and jeans are there? 4 x 3, and for each of those combinations you could have any of the 7 tee shirts, so 4x3x7.
I still don’t get why you have to multiply them , I’m sorry can u just explain it a bit more about why u have to multiply rather than add ?
4. (Original post by ghostwalker)
First off 7x3x4 is the same as 7C1 x 3C1 x 4C1, and you could do it via combinations.

So, why multply rather than add?

Because for each choice of one item, you could have any of the other items.

E.g. for one particular choice of shoes and jeans you could have any of the 7 tee shirts.
For another choice, again you could any of the 7
How many combinations of shoes and jeans are there? 4 x 3, and for each of those combinations you could have any of the 7 tee shirts, so 4x3x7.
For example when do we use the add ? If it were add
5. exam solutions has a video that shows you why.
I'll see if I can find it for you.
6. (Original post by RuthieG101)
exam solutions has a video that shows you why.
I'll see if I can find it for you.
Please tell me if u do find it , I really need the answer. Are u studying statistics too?
7. (Original post by Sammysammy99)
I still don’t get why you have to multiply them , I’m sorry can u just explain it a bit more about why u have to multiply rather than add ?
Lets look at a simpler case.

Suppose you have 3 types of socks - 1,2,3 - and 4 pairs of jeans - a,b,c,d. How many outfits can you make?

1a, 1b,1c, 1d,
2a, 2b, 2c, 2d,
3a, 3b, 3c, 3d.

That is 3 x 4 = 12 in all.
8. (Original post by ghostwalker)
Lets look at a simpler case.

Suppose you have 3 types of socks - 1,2,3 - and 4 pairs of jeans - a,b,c,d. How many outfits can you make?

1a, 1b,1c, 1d
2a, 2b,2c,2d,
3a,3b,3c,3d.

That is 3 x 4 = 12 in all.
I get it now ! Thank you very much . That was really helpful !!
9. im taking s1 in June to finish my a level.

it's for binomial distribution, but shows where all the choices come from
10. (Original post by RuthieG101)
im taking s1 in June to finish my a level.

it's for binomial distribution, but shows where all the choices come from
Thank you so much again , you are very kind !
11. no problem.
I happened to watch it while avoiding my textbook.
his website is recommended too. he has loads!!

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