Daily Math Puzzle: 2026-09-15

6 — The secret rule is to count the number of *distinct* letters in the animal's name. Letters that repeat in a name are only counted once. - LION has L, I, O, N (4 distinct letters). - GIRAFFE has G, I, R, A, F, E (6 distinct letters). - ELEPHANT has E, L, P, H, A, N, T (8 distinct letters). - ZEBRA has Z, E, B, R, A (5 distinct letters). - CROCODILE has C, R, O, D, I, L, E (7 distinct letters from C, R, O, C, O, D, I, L, E). - KANGAROO has K, A, N, G, R, O (6 distinct letters from K, A, N, G, A, R, O, O). Applying this rule to 'PENGUIN': The distinct letters are P, E, N, G, U, I. There are 6 distinct letters. Therefore, the number to be written down is 6.