Motion: Solving problems using equations

[tryintosurviv]

Im sorry if this is in the wrong area ! and I know that this is the easiest question in the history of physics but I need help. I think some of the answers in the back of the text are wrong but I might be just the biggest idiot on the face of the Earth so feel free to point that out. anyways ...

Homework Statement

If 100m sprinters accelerate from rest for 3.5 s at 2.8 m/s (squared) , how far have they ran to this point ? How long will it take them to complete the 100m sprint , assuming they maintain their speed the rest of the way ?

Homework Equations

d= v1t + 1/2a t (squared)

I think ?

The Attempt at a Solution

= 3.5 + 1/2 (2.8)(3.5) squared
= 3.5 + 1/2 (2.8)(12.3)
=3.5 + 34.2 divided by 2
= 3.5 + 17.2
= 20.7 sorry I don't have the division sign or superscript

and I can't do the rest of the question without having the first answer correct. The text says the answer is 17 m


HELP ! Please help a huge idiot

 

[Doc Al]

Hint: What's the initial speed? (What you call v1.)

 

[tryintosurviv]

Isn't it 0 m/s ? It says from rest

 

[Doc Al]

Isn't it 0 m/s ? It says from rest

Exactly! Do you see what's wrong with your calculation now?

 

[tryintosurviv]

OH wow that's great. I was adding instead of multiplying ! Thanks