An average non-mathematical person would say, "I dunno, a million?"

A narrow-thinking engineer answer would start calculating the volume of a golf ball (a sphere 1.68 inches in diameter), the approximate volume of the interior of a school bus (35 feet long, 8 feet wide, 6 feet high), and make a rough estimate of somewhere around 600,000.

An engineer with a little more savvy would ask, "How are the golf balls packed?" "What kind of school bus is it? Does it go to the 'special' school?" Or maybe, "How many students are already on the bus, and how many of them are carrying French horns?" (Disclaimer: I had to carry a French horn to school on the bus during junior high school, and nothing makes you a school bus don't-sit-next-to-me pariah like a French horn.)

The smart-aleck answer to this is, "all of them, if you carry them on one at a time". I actually like that answer; it points out the ambiguity in the question.

The point of this question is this: there are multiple interpretations to the question, and there are many parameters that have not been explicitly spelled out. If you answer the question quickly, without getting all the facts, you are not thinking critically.

If you put all the golf balls in the world in to an incinerator...also would like to know if they're regulation golf balls or the european sized ones, which are smaller!

3000000 OR MORE

The answer is "Who cares?"