How do you say 7C4 in words?

Question

I would like to know!

its a factorial or something.

Answer 1

it means "a combination of 7, taken 4 at a time

in other words, if you have seven numbers and use any four of them at any given time, how many combinations can you make?

1234

1235

1236

1237

2345

2346

etc etc

note though, a combination means a group of numbers in any combination so 1234 is the same as 4321.

a permutation means that the order counts.

so a combination lock should really be called a permutation lock....

Answer 2

"Seven choose four" is what you're looking for. It's combinatorics.

The value of that represents the number of different ways one could choose four objects out of seven. Its value can be calculated using factorials, like you suggested, to be n! / [k! * (n-k)!], where nCk.

In this case, it would be 7! / [4! * 3!] = 35.

Answer 3

Looks like "seven sea four" to me ....

OR "seven choose four" (out of 7 things, choose 4)

Answer 4

It is actually part of probability called a combination.  The 7 and the 4 are usually subscripted.

It is pronounced "7 choose 4", and means you have 7 items, and randomly pick 4, how many possible groups of 4 can you get?

It is equal to 7!/[4!*(7-4)!]

Factorial means 1*2*3*4*5*....all the way up to the number.  It is usually written backwards (counting down to 1).

So 7! = 7*6*5*4*3*2*1 = 5,040

So 7C4 = 7!/[4!*(7-4)!]

= 7*6*5*4*3*2*1/[4*3*2*1*(3*2*1)!]

= 7*6*5/(3*2*1)

= 7*5

= 35 (if you have 7 items, and you pick 4 at a time randomly, there are 35 different ways you can pick those 4)

Combinations do not care about duplicates.  So for instance if you have 7 balls, numbered 1, 2, 3, 4, 5, 6, 7, and you draw out "1, 2, 3, 4" randomly, that is the same thing as having drawn out any of the following balls in this order:

1, 2, 3, 4

1, 2, 4, 3

1, 3, 2, 4

1, 3, 4, 2

1, 4, 2, 3

1, 4, 3, 2

2, 1, 3, 4

2, 1, 4, 3

2, 3, 1, 4

2, 3, 4, 1

2, 4, 1, 3

2, 4, 3, 1

3, 1, 2, 4

3, 1, 4, 2

3, 2, 1, 4

3, 2, 4, 1

3, 4, 1, 2

3, 4, 2, 1

4, 1, 2, 3

4, 1, 3, 2

4, 2, 1, 3

4, 2, 3, 1

4, 3, 1, 2

4, 3, 2, 1

If you drew out the balls in any of those orders, they would be counted as having just drawn out 1, 2, 3, 4.

Permutations do care about order.  7P4 = 7!/(7-4)! = 840

Answer 5

Combination of 7 taken 4 at a time.

Answer 6

yes,    7C4=7!/(4!(7-4)!)=35