Twenty-five chits numbered 1 to 25 are folded and mixed in a bowl. One chit is picked at random. What is the probability that the number on it is a factor of 24?

The factors of 24 are 1, 2, 3, 4, 6, 8, 12 and 24, and every one of them is 25 or less, so 8 chits are favourable. $P=\frac{8}{25}.\frac{7}{25}$ leaves out 24 itself, which is a factor of 24; $\frac{6}{25}$ stops at 8 and misses 12 and 24; $\frac{1}{5}$ lists only 1, 2, 3, 4 and 6.