Melody

Obviously the sides have to add to 20 and they have to be integers.

the only other rule is that the 2 little sides have to add to be more than the length of the 3rd side

The longest one cannot be 19 the two little ones cannot add to 19

Can the longest one be 18?

work your way down and work out what triples can work.

Give it a go yourself  :))

Thanks Alan   

What is the little symbol at the beginning?

¬(x>-2) = ?

That is a really neat proof!   Thanks guest.

ok, thanks   But I would prefer to describe it as

11! /(5! * 3! * 3!)   divide by 2 because the 3! and 3! are interchangeable. multiply by 2 because there are 2 ways to add in Henry.

=  9,240 ways

I am still having some trouble thinking about it this way though. 

This would normally be the answer to a question like this.

How many ways can the 11 letters  aaabbbcccc be arranged in a line.   11!/(3!3!4!)  is the answer.    [I am not going to concern myself with Henry]

For our question it would be how many ways can 11 objects be put in a line if the order of the first 5 does not matte, the order of the next 3 does not matter and the order ot the last 3 does not matter AND the second and third groups of 3 can be swapped around. 

NOW it does make sense to me.    11!/(3!3!4!) divided by 2

Thanks guest for making me think about that.

Thanks for letting everyone know iloty.

The job you took on is indeed very time consuming.

Good luck with all the things you are doing and we see you when your life quietens down.

Ron is a good username for you :)

There is 360 degrees in a full revolution and 5 sides to a pentagon.

So the minimum would be 1/5 of a revolution.

I never suggested that EP was wrong.

If this was a school question here, the student would be expected to use a GP. 

If it was a consumer finance question at a college then they would use the formula.

Hi Naci,

This question is very poorly worded. The meaning must be guessed.

My guess:

An annuity pays 3.9 % (yearly and nominal (the effective rate is a little higher), compound monthly.

What equal monthly deposit should be made into this annuity in order (at the beginning of each month?) to have $79,000 at the end of 18 years?

Anyway:

Your answer is far too simplistic. The money is going into an account each month and staying there for for 18 years.

18*12=216months      3.9/12=0.325% = 0.00325 interest per month

Assuming that the first installment is paid AT THE BEGINNING of the first month AND P dollars are deposited each month, then

the first deposit will grow to    P(1.00325)^216

the second deposit will grow to    P(1.00325)^215

...

the last deposit will grow to  P(1.00325)^1

You know that this will add to $79000 so you can solve it as a GP (assuming you know about GPs geometric progressions)

There are also formulas, that I have forgotten,  EP has used a financial mathematics formula.