A running track, 5 meters wide, has the dimensions shown in the diagram. The ends of the track are semicircles with diameter 20 meters. What is the surface area of the track? -100 meters - 20 meters

Elementary Geometry For College Students, 7e
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Author:Alexander, Daniel C.; Koeberlein, Geralyn M.
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**12. A running track, 5 meters wide, has the dimensions shown in the diagram. The ends of the track are semicircles with a diameter of 20 meters. What is the surface area of the track?**

**Diagram Explanation:**
- The diagram shows a top-down view of a running track.
- The track has straight sections of 100 meters in length, connected by semicircular sections at each end.
- Each semicircle has a diameter of 20 meters.
- The width of the track around its length is 5 meters.

**Steps to Solve:**

To find the surface area of the track, we need to consider both the rectangular and semicircular parts of the track and then account for the overall width across its dimensions. 

**Calculate the area of the rectangular part:**
- Length: 100 meters
- Width: 20 meters (as the diameter of semicircles determines the rectangle's width)

\[ \text{Area of rectangle} = \text{Length} \times \text{Width} = 100 \, \text{meters} \times 20 \, \text{meters} = 2000 \, \text{square meters} \]

**Calculate the area of the semicircular parts:**
- The total length of the semicircles is equivalent to one full circle since there are two semicircles.
- The radius of the semicircles is 10 meters (since the diameter is 20 meters).

\[ \text{Area of a full circle} = \pi \times (\text{radius})^2 = \pi \times (10 \, \text{meters})^2 = 100\pi \, \text{square meters} \]

**Calculate the total area of the track:**
- Sum the area of the rectangular part and the area of the semicircular parts:

\[ \text{Total Surface Area} = \text{Area of rectangle} + \text{Area of full circle} = 2000 \, \text{square meters} + 100\pi \, \text{square meters} \]

Let's take π ≈ 3.14 for an approximate numerical result:

\[ 100\pi \, \text{square meters} ≈ 100 \times 3.14 = 314 \, \text{square meters} \]

\[ \text{Total Surface Area} ≈ 2000 \,
Transcribed Image Text:**12. A running track, 5 meters wide, has the dimensions shown in the diagram. The ends of the track are semicircles with a diameter of 20 meters. What is the surface area of the track?** **Diagram Explanation:** - The diagram shows a top-down view of a running track. - The track has straight sections of 100 meters in length, connected by semicircular sections at each end. - Each semicircle has a diameter of 20 meters. - The width of the track around its length is 5 meters. **Steps to Solve:** To find the surface area of the track, we need to consider both the rectangular and semicircular parts of the track and then account for the overall width across its dimensions. **Calculate the area of the rectangular part:** - Length: 100 meters - Width: 20 meters (as the diameter of semicircles determines the rectangle's width) \[ \text{Area of rectangle} = \text{Length} \times \text{Width} = 100 \, \text{meters} \times 20 \, \text{meters} = 2000 \, \text{square meters} \] **Calculate the area of the semicircular parts:** - The total length of the semicircles is equivalent to one full circle since there are two semicircles. - The radius of the semicircles is 10 meters (since the diameter is 20 meters). \[ \text{Area of a full circle} = \pi \times (\text{radius})^2 = \pi \times (10 \, \text{meters})^2 = 100\pi \, \text{square meters} \] **Calculate the total area of the track:** - Sum the area of the rectangular part and the area of the semicircular parts: \[ \text{Total Surface Area} = \text{Area of rectangle} + \text{Area of full circle} = 2000 \, \text{square meters} + 100\pi \, \text{square meters} \] Let's take π ≈ 3.14 for an approximate numerical result: \[ 100\pi \, \text{square meters} ≈ 100 \times 3.14 = 314 \, \text{square meters} \] \[ \text{Total Surface Area} ≈ 2000 \,
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