A store sells pencils and erasers. It has a rule that for every pencil you buy, you must buy 2 erasers which cost 1/2 the price of the pencils. If they sold 20 pencils and earned $80, how much do erasers cost? Let's be accurate as possible.
They sold 40 erasers because 20 x 2 = 40. Therefore 20(Pencil Price) + (1 / 2)(40 x Pencil Price) = 80. Therefore 40(Pencil Price) = 80. Therefore (Pencil Price) equals 2 because 80 / 40 = 2. An eraser costs $1 because 2 / 2 = 1.
The answer: 1.