Question

Need help with a word problem.

Answer 1

Well what is it?

Answer 2

Well I think that the answer is 42.

Answer 3

A person standing close to the edge on the top of a 309-foot building throws a baseball vertically upward. The quadratic equation h = -16t^2 + 64t + 309 models the ball's height \, h \, above the ground in feet, t seconds after it was thrown.

Answer 4

How many seconds does it take until the ball finally hits the ground? Round to the nearest tenth of a second.

Answer 5

Okay, yes. We all know you've read/heard off Hitchhiker's Guide.

Answer 6

So...presumably, I begin by substituting -309 for h?

Answer 7

No?

Answer 8

Well yes... I am putting it into a calc
309 = -16t^2 + 64t + 309
I got 0 and 4. Maybe wrong tho....

Answer 9

Yep i am right

Answer 10

Just entered in that answer, and it's apparently wrong.

Answer 11

How? I entered it and got it right!

Answer 12

It'd probably be a good idea to try doing it on paper, rather than with a calculator.

Answer 13

0 definetly works.

Answer 14

h = -16t^2 + 64t + 309
309=-16t^2 + 64t + 309
309=-256 + 256 +309
309=309
t=4

Answer 15

http://www.quickmath.com/webMathematica3/quickmath/equations/solve/basic.jsp#c=solve_basicsolveequation&v1=309+%3D+-16t%5E2+%2B+64t+%2B+309+&v2=t

Answer 16

Wait..what? How are you getting -256?

Answer 17

Where did the t go?

Answer 18

i subbed t for 4

Answer 19

That was a proof that t=4

Answer 20

-16(4)^2 = -265

Answer 21

No, no. You need to substitute -309 for h, not 309.

Answer 22

4^2 is 16
16 times -16 is -256

Answer 23

Get it? Btw 0 cancels everything out except 309 so thats y it works.

Answer 24

wait -309?

Answer 25

Yep.

Answer 26

The equation says h but whatever. Actually I dont think so man. Here is the equation with -309 for h : http://www.quickmath.com/webMathematica3/quickmath/equations/solve/basic.jsp#c=solve_basicsolveequation&v1=-309+%3D+-16t%5E2+%2B+64t+%2B+309+&v2=t

Answer 27

I am using your original equation and it all fits. Otherwise if h is negative then it is -4.52878 and 8.52878

Answer 28

Okay, 8.5 is apparently wrong and -4.5 seconds isn't a viable response, but thank you for your help.

Answer 29

Sorry if i got it wrong. What math is this? Like pre-alg or alg or calc etc

Answer 30

Alg.

Answer 31

Benn a while then. I am in Alg 2 honors. Must be wrong or something but I tried my best. Still think the answer is 42 ;)

Answer 32

lol I haven't tried that yet. Perhaps so!

Answer 33

This is quite confusing. What does the complete question say?