## Prealgebra (7th Edition)

$12^2+x^2=24^2$ $144+x^2=576$ $x^2=432$ $\sqrt {432}=x$ $\sqrt {432}\approx20$ Divide and average to refine the approximation. $432\div20=21.6$ $(20+21.6)\div2=20.8$ Repeat to further refine. $432\div20.8=20.77$ $(20.8+20.77)\div2=20.785$