some exersise books have to be arranged in piles with 10 or 15 or 20 books per pile . what is the least number of books needed to do this?

Polynomial that can be factored as (3x-4)(3x+4)

Perry observes the opposite parallel walls of a room in how many lines do the plains containing the walls intersect

Our star pitcher, foster enlight, can throw a pitch so fast that it gets to the catcher’s mitt before it leaves foster’s fingers! if the team wins a game then the probability that foster was pitching is 0.8 but only if foster had at least one day’s rest since his last pitching assignment. if foster does not have a day off and the team still wins, the probability that foster was pitching drops by half of what it was on the previous day. if the team wins three games in succession from the toronto tachyons and foster pitched in game #2, what is the probability that he pitched in one or more of the other games? (assume that foster did not pitch on the day before the first game of this three game series.)