Chapter 15: The Civil War What do you think were the key factors that allowed the United States to defeat the Confederate States of America? Was it economic factors, military victories or other factors? What were some of the key events, battles and turning points of the Civil War?

Chapter 16: The Era of Reconstruction, 1865–1877.

Consider social, political, and economic equality during the Reconstruction era. What were some of the key successes of Reconstruction? What were some of the important limitations to the progress made during this era?

a. The light travels 4,500,000 kilometers in 15 seconds

b. It takes the light 40 seconds to travel 12 million kilometers

Step-by-step explanation:

- The function d(t) = 300,000 t represents the distance in kilometers

  that light travel in t seconds

a.

- We need to find how far the light travels in 15 seconds

∵ d(t) = 300,000 t

∵ t = 15 seconds

- Substitute the value of t in the function above

∴ d(t) = 300,000 (15)

∴ d(t) = 4,500,000 kilometers

The light travels 4,500,000 kilometers in 15 seconds

b.

- We need to find how long does it takes the light to travel 12 million

  kilometers

∵ d(t) = 12 million kilometers = 12,000,000 km

∵ d(t) = 300,000 t

- Substitute the value of d(t) in the function

∴ 12,000,000 = 300,000 t

- Divide both sides by 300,000

∴ t = 40 seconds

It takes the light 40 seconds to travel 12 million kilometers