Quadratic Equations- applications

[damzel]

I had hw and i got stuck on two questions. Can somebody help, me and my roomate are stuck on these questions.

1) The average cost of a wedding, in dollars, is modeled by C(t)= 38t^2 + 291t +15,208
where t=0 represents the year 1990 and 0<t<14.Use the model to determine the year during which the aerage cost of a wedding first reached 19,000.
Apparently the answer is 1996, but when i solved it i got huge numbers. Any one know how to solve this problem?

2) A model rocket is launched upward with an initial velocity of 220 feet per second. The height, in feet, of the rocket t seconds after the launch is given by h= -16t^2 + 220t. How many seconds after the launch will the rocket be 350 feet above the ground.? Round to the nearest tenth of a second.

 

[stapel]

1) The average cost of a wedding, in dollars, is modeled by C(t)= 38t^2 + 291t +15,208
where t=0 represents the year 1990 and 0<t<14.Use the model to determine the year during which the aerage cost of a wedding first reached 19,000.

You are given a formula for the cost C at time t, and are given a value for C. Try plugging that value in for C, and then solving the resulting quadratic equation. You can use any of the various methods you've learned, such as the Quadratic Formula that you've memorized. :idea:

Apparently the answer is 1996, but when i solved it i got huge numbers.

Since you did not show your work, I'm afraid we are unable to find your error(s). Sorry!

2) A model rocket is launched upward with an initial velocity of 220 feet per second. The height, in feet, of the rocket t seconds after the launch is given by h= -16t^2 + 220t. How many seconds after the launch will the rocket be 350 feet above the ground.?

You are given a formula for the height h at time t, and are given a value for h. Try plugging that value in for h, and then solving the resulting quadratic equation. :wink:

If you get stuck, please reply showing your work and reasoning. Thank you!

Eliz.