Unit 2 · Number Theory
Pick Three Straws — Odd Total?
Lesson 13 of 18
About this lesson
Label each straw E (even) or O (odd). For 3 numbers to add to an ODD total, you need either 3 odds or 1 odd + 2 evens. Count valid combos from each case — no need to add the actual numbers.
Chapters
Question
Michael has five straws with lengths 2 cm, 5 cm, 8 cm, 11 cm and 14 cm.
He wants to choose three of the straws, so that their lengths add up to an odd number of centimetres.
In how many different ways can Michael do this?
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