John is installing five solar panels on the roof of his house. The width of each panel is between 2 feet and 4 feet, and the length of each panel is between 3 feet and 6 feet. John estimates the total area of the five panels to be 140 square feet. Is this a reasonable estimate?

The width is between 2 feet and 4 feet
Taking the average, 1/2 (2 + 4) = 4 feet

The length is between 3 feet and 6 feet
Taking the average, 1/2 (3 + 6) = 4.5 feet

Area of one panel = 4 x 4.5 = 18 ft²
Area of 5 panels = 18 x 5
Area of 5 panels = 90 ft²

The estimated area of the 5 panels is 90 ft².

John's estimate is not reasonable as 140ft² is way too high from the average of 90 ft².

Even taking the biggest possible length and width
The area of 1 panel = 4 x 6 = 24 ft²
The area of 5 panels = 24 x 5 = 120 ft²
Even taking the highest possible estimate of 120 ft², John's estimate is still way too high