Melody

You already asked this queston here.  

If you are refering to number sequences and not numbers then the first digit can be zero.

In which case you have

10*10=100 ways

If you are talking numbers then the first digit cannot be zero so it will be

9*10 =90

Since you have seen the probable cause of the error can you now fix it yurself?

Please thank the answerer for their interest and never say that an answer is incorrect without giving a reason.

The reason can be very simple. ....     Like

My teacher says it is wrong,

or

The answer in the back of the book is such and such.

Always give the answerers as much knowledge about the question as what you have yourself.

Guest, are you and  madyl the same person.

It is confusing when you do not identify yourselves properly.

Nevermind, thanks for the input.

I also have only done part A

That solution in mathsisfun is very confusing, I am not surprised that people cannot follow it.

Hopefully I will put aside some serious time and effort for this question later.  I just have to find that time and drive which might be difficult.

Someone else might answer first. 

CPhill is usually pretty good with these and Omi67 does a lot of geometry questions too I think.

I never would have guessed that, thanks Chris.

I count 10 too

Thanks for responding Madyl,

Do you mean you have worked out all three for yourself?

If you have then that is excellent !

Do you have the address for the mathsisfun solution? 

I just think if may be laid out more simply than guests copied version.

ok that is fine.

If what you say is correct then he/she was plaguizing.

You should have just accused him outright rather than asking him if he was guilty.

That does explain you attitude, thanks for that explanation.

He/she should not be rewared for plaguizing.

a) There is a circle propery that just says that the 2 tangential distances from an external point to a circle are equal.

Using this   AM=AP   and   BM=PM

so    AM=MB 

so if M is on AB it follows that M is the midpoint of AB

I haven't done the other 2. They would take more effort on my part.  Are you happy with my part A?

Nine friends sit around a circular table. Two of the friends, April and Dave, want exactly two people to be between them. How many different seatings are possible? (As usual, two seatings are considered the same if one is a rotation of the other.)

Sit the two friends. Two ways.

There are 7 places left 

I believe that the answer is  2*7! = 10080 permutations.