Answer:
The football field is 4320 inches long.
Explanation:
Since we're told that 12 in = 1 ft and 3 ft and 1 yd, we can first convert 120 yards to feet and then convert to inches using proportions:
Converting 120 yards to feet:
120 yards / x feet = 1 yard / 3 feet
(120/x = 1/3) * x
(120 = 1/3x) / (1/3)
(120 = 1/3x) * 3
360 = x
Thus, 120 yards is the same as 360 ft.
Converting 360 feet to inches:
360 feet / x inches = 1 foot / 12 inches
(360 / x = 1/12) * x
(360 = 1/12x) / (1/12)
(360 = 1/12x) * 12
4320 = x
Thus, the 120-yard long football field is 4320 inches long.