Free interactive math game: Find Composite / Prime — Pick from a set. Part of the Divisibility & Numbers category on MathKite.
Taken from the generator that powers this exercise. A fresh set appears every time the page is opened, and the printable worksheet holds ten of them.
Picking out the composite or the prime from a set of numbers.
Run the quick divisibility tests over each option. A single divisor other than one and itself settles the matter.
Among 11, 13, 15 and 17 only 15 divides by 3 and 5, so 15 is the composite one.
Assuming odd means prime. 9, 15 and 21 are all odd and all composite.