Question
An octagon has a side length of 15 feet and an area of 1089.6 ft²
Find the area of a smaller octagon that has a side length of 7 feet.
Answer:
237.3ft²
Step-by-step explanation:
We are given two octagons in the above question.
Side length of larger octagon = 15 ft
Area of larger octagon = 1089.6 ft²
The area of a smaller octagon = X
Side length of smaller octagon = 7 ft.
We solve for this using scale factor
Scale factor(k) = ratio of the side length of the octagon = smaller side length/ larger side length
k = 7/15
It is important to note that
The square of the scale factor k = ratio of the areas of the octagon
Hence,
k² = X/1089.6 ft²
(7/15)² = X/1089.6 ft²
7²/15² = X/1089.6 ft²
Cross Multiply
15² × X = 7² × 1089.6ft²
X = 7² × 1089.6ft²/15²
X = 237.29066667ft²
Approximately, the area of the smaller octagon = 237.3ft²
