Question

Raul has to choose 3 of the 5 toppings for his frozen yogurt. How many different combinations of toppings are possible? A. 10 B. 20 C. 60 D. 120

Answer 1

This is just 5 choose 3

Answer 2

Do you know how to calculate choose?

Answer 3

No..lol

Answer 4

n choose k = n! / ( k! (n-k)! )

Answer 5

So 5 choose 3 = 5! / (3! 2!)

Answer 6

That is confusing, I don't understand.

Answer 7

Do you know what 5! is?

Answer 8

No. I don't know how to do that, is it 5x4x3x2x1?

Answer 9

They properly didn't prepare you for this question.

Answer 10

Yes, that is correct 5! = 5x4x3x2x1

Answer 11

Okay so I just plug that into the whole equation?

Answer 12

So now you need to do 3! and 2!

Answer 13

Then add them all together?

Answer 14

then plug them into 5! / (3!2!)

Answer 15

I'm still confused...

Answer 16

Okay what is 5!?

Answer 17

I have already did that, the equation doesn't make sense.

Answer 18

okay it is 5! / (3! x 2!)

Answer 19

Multiply bottom ones, then divide the result from 5!

Answer 20

Is it 60? I'm on a timed practice.

Answer 21

no.

5! = 120, 3! = 6, 2! = 2
5 choose 3 = 120 / (6 * 2) = 120 / 12 = 10

Answer 22

Thank you.