The area of the football field is 57,600 square feet. If the width of the field is 4/9 the length, what is the length of the football field ?

360 feet.

Step-by-step explanation:

Let x = length, then the width is 4x/9 feet.

So we have the equation:

x * 4x/9 = 57600

4x^2 / 9 = 57600

4x^2 = 57600 * 9

x^2 = 57600 * 9 / 4

x = √57600 * 3 / 2

x = 240* 3/2

x = 360 feet.