A right angle is 90°.

Pythagorean triples are three whole number sides that form a right triangle. In one such triangle, 54-72-90, the longest side, 90, is opposite the 90° angle!

In seven other right triangles, side 90 is adjacent to the 90° angle:

- 48-90-102
- 56-90-106
- 90-120-150
- 90-216-234
- 90-400-410
- 90-672-678
- 90-2024-2026

90 is a composite number. 90 = 1 x 90, 2 x 45, 3 x 30, 5 x 18, 6 x 15, and 9 x 10. Factors of 90: 1, 2, 3, 5, 6, 9, 10, 15, 18, 30, 45, 90. Prime factorization: 90 = 2 × 3 × 3 × 5 which can also be written 2 × 3² × 5.

Sometimes 90 is a clue in the FIND THE FACTORS 1 – 12 puzzles. Even though it has other factors, we only use 90 = 9 x 10 in the puzzles.

This week’s puzzles and last week’s solutions: 10 Factors 2014-04-14