On a sunny day, cindy notices that her shadow is 21 inches long. if it is 75 inches from the top of her head to the end of the shadow, how tall is cindy?

Cindy is 72 inches long. Imagine it like a right triangle. Her shadow is the base, she is the side, and the distance between her head and the end of the shadow is the diagonal line connecting the two. Use the Pythagorean theorem to find how tall cindy is.

a²+b²=c²        a=21, the length of the shadow
                       b= ? cindy's height
                     c= 75, the distance from her head to the edge of the shadow
21²+ b²=75²
441 +b² = 5625
-441         -441
        
  0             5184
b² = 5184
√b² =√5184
b= 72

hope it helps