Problems of the 2nd tour


Theme : Combinatorics (difficulty level : easy)

Name Age Country Problem
Problem 1 N.P 17 France An unknown coded alphabet contains 6 vowels and 8 consonants. To form a word, we have to alternate the vowels and the consonants. How many words of 9 letters can be formed with this alphabet?
Problem 2 N.P 17 France How many are there 9-digit numbers which the sum of figures is even ?
Problem 3 N.P 17 France A natural number is said "nice" when its written contains only odd digits. How many are there 4-digit "nice" integers ?

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