Four books, one each on physics, chemistry, mathematics, and biology are about to be stacked on a shelf. If the books are stacked randomly, what is the probability the mathematics book is on top?
There are 4 books. The math book can either be top, second from top, third from top, or on the bottom. The probability of being in any single given position is 1/4 = 25% .
Since each book can be put on the top, and there are 4 books, the chances of a math book going on the top is 1/4, while the other 3 chances are the other books. So your answer is 1/4 or 0.25
