A school has 1,250 pupils on its rolls, of whom 750 are boys. On a rainy Monday 18% of the boys and 24% of the girls stayed away. How many pupils attended school that day?

Boys away = 18% of 750 = 135. The girls number 1250 - 750 = 500, so girls away = 24% of 500 = 120. Total away = 135 + 120 = 255, leaving 1250 - 255 = 995 present. 980 swaps the two rates (24% of the boys, 18% of the girls, giving 270 away). 1,025 applies the 18% to all 1,250 pupils. 255 is the number who stayed away, the opposite of what was asked.