You will need to set up a proportion to find the height of the child.

48⁄72 = x⁄6

The ratio on the left side of the proportion represents the height of the water tower(48 ft) compared to it's shadow(72 ft). The ratio on the right side of the proportion represents the height of the child (x ft) compared to the child's shadow(6 ft).

Once you have the proportion set up, cross multiply to form the following equation: 48 • 6 = 72 • x. To solve the equation, multiply 48•6 and then divide by 72. Hope this helps!!!