# Project Euler Problem 17 in F#

Project Euler problem 17 turned out to be quite an easy one.

If the numbers 1 to 5 are written out in words: one, two, three, four, five, then there are 3 + 3 + 5 + 4 + 4 = 19 letters used in total.

If all the numbers from 1 to 1000 (one thousand) inclusive were written out in words, how many letters would be used?

NOTE: Do not count spaces or hyphens. For example, 342 (three hundred and forty-two) contains 23 letters and 115 (one hundred and fifteen) contains 20 letters. The use of "and" when writing out numbers is in compliance with British usage.

## Solution

The solution this time is almost trivial:

• "Zero" is considered to have 0 length (it will be obvious later on why this is the case)
• Numbers from 1 to 19 have their own unique names (i.e. they are not composed by putting together more words)
• Numbers from 20 to 99 are combined putting together a word like "thirty" and a number from 0 to 9. If the number is zero, we don't add anything (we don't say "twenty and zero")
• Numbers from 100 to 999 are combined putting together a words like "two hundred and" plus a number from 0 to 99 composed as explained above. Exact multiples of 100 are exception in that they don't have another trailing number (again, we don't say "two hundred and zero").

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