When do you use multiplying and dividing fractions in the real world?

Answer 1

You may not literally say "multiplied by a half" but multiplying and dividing by fractions are equivalents to doing the other function with an inverse number, most easily in that dividing by 2 is the same as multiplying by (1/2). We don't often multiply and divide by fractions because most of the time we can convert such a problem into a nicer one.

We may use fractions like this, for example, in a test out of 90 marks where one must score 2/3 to pass. This pass mark is obtained by multiplying 90 by (2/3), though this, as said earlier, would usually, even unconsciously with such convenient numbers, be split into "divide by 3, then multiply by 2".