Question

Hi, I would like to know what's the easiest way to identify a permutation and combination and distinguish between the two

Answer 1

the most obvious way is... permutation uses the word "arrange"..combination uses the word "select"

Answer 2

Ok seems easy enough. Could you provide an example. I have already practiced a few but seem to mix them up a lot.

Answer 3

Let's try something basic...

How many 5 letter arrangements can be made from the letters of DRAGON

Answer 4

oops wait needs to be 6!

Answer 5

are you talking to me or estudier?

Answer 6

Igbasallote

Answer 7

Dragon will be 6! = 1x2x3x4x5x6 ways the letters can be arranged

Answer 8

right, but note: i said 5 letter arrangements

Answer 9

ok let me work that out by using the permutation formula.

Answer 10

sure

Answer 11

6P5 thus 6 being a set of 6 object and 5 being k number of objects in the set.

Answer 12

right

Answer 13

would you like something that involves more thinking?

Answer 14

Yes the worse the better. always get the worst in exams.

Answer 15

A car license plate consists of 3 letters followed by a 3-digit number. How many license plates are theoretically possible?

Answer 16

The letters are currently not specified so it can be a - z and this is not dependent on order. (So the first part of the numberplate is a combination). The second part of the numberplate is also not dependent on order making it a comination.

Answer 17

close...but one part is wrong

Answer 18

the second part is somehow dependent on order....note: somehow

Answer 19

Ill have to work out the different combinations letters can be arranged in and the numbers can be arranged in. and the total possible number plates that can exit with these two items together.

Answer 20

The order of the numbers and letters are important

Answer 21

well no...order isn't that important...since it already stated the order, you can't solve for order anymore

Answer 22

i just said order is somehow important for the second part because for the 3-digit number, you can't start with 0

Answer 23

do you get what i mean?

Answer 24

yes.

Answer 25

wonderful

Answer 26

I'm just sitting at work @ the moment but ill be able to work it out tonight.

Answer 27

Which part did i not get right ? in South - Africa number plates can start with a zero

Answer 28

the part when i said that it is a 3-digit number...true a license plate can start with 0. however, a number cannot start with 0

Answer 29

and since my condition was that it's a 3-digit number, you don't start with 0. make sense?

Answer 30

Ah i see, So the first part of 3 letters will be worked out as a combination and the second part containing the digits will be worked out as a permutation.

Answer 31

I missed the Number... description in word puzzle.

Answer 32

it's still combination...you just consider 9 numbers for the first digit rather than 10 numbers

Answer 33

mmmm. yea also thought of that :(

Answer 34

if i have worked out the combination of the two parts do i sum add these to totals together ?

Answer 35

no. you multiply

Answer 36

Ok, it would be nice if you could provide me with a description why i should multiply ?

Answer 37

So answer will be :(Combination of first Letters 26C3) x ( Combination of 3 Digits 9 C 3)

Answer 38

i see why you're confused...

Answer 39

let's draw some blanks



agree?

Answer 40

then...there are 26 letters of the alphabet yes?

Answer 41

yes

Answer 42

so in each blank, 26 letters can be placed

and you know...you multiply these

Answer 43

following so far?

Answer 44

yes.

Answer 45

so what do you think do you do for the second part?

Answer 46

The number 9 will be added and multiplied.

Answer 47

added?

Answer 48

Will be added to the empty field in the bubble and be multiplied. The Digits and Letter amounts will then be added together for a total of 18305

Answer 49

yea i have a feeling i am getting this wrong

Answer 50

added together?? i've told you many times you don't add...you multiply...you'll only add if you see the word "or"