An easy way to think of it is discrete data is counted whereas continous data is measured. You measure brake time and don't count it, therefore it is continous.
(1/2) / (1/4) = 1 / x......1/2 wall to 1/4 hr = 1 whole wall to x hrs cross multiply (1/2)(x) = (1/4)(1) 1/2x = 1/4 x = 1/4 * 2 x = 2/4 reduces to 1/2....so it will take 1/2 hr (or 30 minutes) to paint the whole wall.
