Percentage = Value ∕ Total ×100 Value here is the number of boys (480) The percentage is 80 Let x= total number of pupils in the school ⇒80=480∕x×100 Get rid of the x dividing (fraction) by multiplying both sides of the equation by x ⇒80×x=480×100 Divide both sides of the equation by 80 ⇒x=480×100∕80 80 will go into 480,6 times ⇒x=480×100∕80=6×100=600 Hence there are 600 pupils in the school