A pie chart shows the preferred subject of 720 students. Maths 150°, Science 120°, Arts 60°, Commerce 30°. How many more students prefer Science than Arts?

Science covers 120° of the 360°, that is (120/360) × 720 = 240 students, and Arts covers 60°, that is 120 students, so the difference is 240 − 120 = 120 students. Equivalently the 60° gap is 60/360 = 1/6 of the students, and 720 ÷ 6 = 120. Reading the 60° gap straight off as a count gives 60, and 240 is Science's own total.