Dixon and his little sister Ariadne stand next to each other on the playground on a sunny afternoon. Their mother measures their shadows. Dixon's shadow is 18 feet long and Ariadne's shadow is 15 feet long. If Dixon is 6 feet tall, how tall is Ariadne?

Answer 1

18 / 15 = 6 / x

multiply both sides by 15 x (or "cross multiply")

18 x = 15 * 6

x = 15 * 6/18 = 15/3 = 5 feet

Answer 2

18