Answer: It would take 9 hours for 4 painters to paint 720 feet of fence.
Explanation:
1.) Calculate the time needed to paint the 720 ft fence with 2 painters.
a.) Divide 720 by 280 to get how many times greater 720 is than 280.
720 / 280 ≈ 2.57
b.) Multiply the time needed to paint the 280 ft fence with 2 painters by 2.57.
7 * 2.57 ≈ 18
2.) Calculate the time needed to paint the 720 ft fence with 4 painters.
a.) Assuming that each painter paints the same amount of fence, divide the time in half, as 4 painters is double the original amount, so it would take half of the time.
18 / 2 = 9