Exponential Word Problems (Sat)

A 78 gram sample of Uranium loses half of its mass each year.  What is the exponential equation? 

• y=78(0.5)^x
• y=78(1.5)^x
• y=78(2)^x

Jimmy purchased a rare coin for $350. It will appreciate (increase) in value by about 6% each year. Write the equation that represents this.

• y=350(0.06)^x

• y=0.06(350)^x

• y=350(0.94)^x

• y=350(1.06)^x

Luke purchased a car for $18,500. It will depreciate (decrease in value) 16% each year. Write an equation to represent the scenario.

• y= 18,500 (1.16)^x

• y= 0.16 (18,500)^x

• y= 18,500 (0.84)^x

• y= 0.84 (18,500)^x

This morning, Kendall drank a cup of coffee that had 95 milligrams of caffeine in it. She didn't have any more caffeine for the rest of the day. Kendall read online that the amount of caffeine in her body will decrease by approximately 13% each hour.

Write an exponential equation in the form y=a(b)x that can model the amount of caffeine, y, in Kendall's body x hours after drinking the coffee.