Question

Antonio is a biologist studying life in a pond. He needs to know how deep the water is. He notices a water lily sticking straight up from the water, whose blossom is 8 cm above the water's surface. Antonio pulls the lily to one side, keeping the stem straight, until the blossom touches the water at a spot 40 cm from where the stem first broke the water's surface. How is Antonio able to calculate the depth of the water? What is the depth?

Answer 1

For this problem we can represent the situation as a rectangle triangle.
 x: depth of water.
 40: Base. "Antonio pulls the lily to one side, keeping the stem straight, until the blossom touches the water at a spot"
 x + 8: Hypotenuse. "He notices water lily sticking straight up from the water, whose blossom is 8 cm above the water's surface." Antonio pulls the lily to one side, keeping the stem straight, until the blossom touches the water at a spot".
 By the Pythagorean theorem we have:
 x ^ 2 + 40 ^ 2 = (x + 8) ^ 2
 Clearing x:
 x ^ 2 + 1600 = x ^ 2 + 16x + 64
 x ^ 2 - x ^ 2 = 16x + 64 - 1600
 0 = 16x -1536
 1536 = 16x
 1536/16 = x
 x = 96
 answer:
 1) x ^ 2 + 40 ^ 2 = (x + 8) ^ 2
 2) the depth of the water is
 x = 96