Ordering Numbers Question #2

[karrotman]

Ok. so I looked at this question an said: "Easy! Typical 5 choose 3 question." So I did:

5!/(5-3)! = 60

CATPREP says I am wrong and provides this bizzare explanation.

Can someone please explain this in a more clear way?



I get that I was wrong. I know that the 3 digit numbers that have a ZERO in front are technically TWO digit numbers. However, I do not see how (4 choose 2) is the amount of 3 digit numbers that have a ZERO in front...)

[karrotman]

Ok. Nevermind. I figured it out. However, I think it's a pretty good question so I'll leave this up.

What you do is find out all of the possible combinations of 2 digit numbers and then put a ZERO in front. This will give you the total 3 digit numbers with a ZERO in front. This is indeed (4 choose 2).

Now subtract all of these possibilities from 60...


Me: Thanks karrotman!

Me: NP dude, you take care.