Need a quick check.

[chibi_lenne]

These are the questions I've been working on and my physics teacher is away and I just need to have someone look these over before I continue on with the position-time, velocity-time, and acceleration-time graphs that I need to make. (His suggestion) Just to make sure that the information I have currently is accurate, or at the very least leaning in the right direction so I can correct them.
*Please excuse the poor quality of the scans*

http://i14.photobucket.com/albums/a315/chibi_lenne/physics1.jpg

http://i14.photobucket.com/albums/a315/chibi_lenne/phsics2.jpg

[Doc Al]

(a) You go from v = \Delta d / \Delta t (correct!) to \Delta t = v \Delta d (incorrect!)
(b) OK
(c) The average speed is \Delta d / \Delta t; what's the average speed?
(d) Use \Delta d = v \Delta t--you made an error similar to what you did in part a. (And don't confuse speed v with change of speed \Delta v.)

[cscott]

You need to use equations for uniform acceleration (v_2^2 = v_1^2 + 2ad or d = v_1t + \frac{1}{2}at^2) for (c) and time should be 5s for (d) since it's only asking the distance past the hill.

[chibi_lenne]

Alright...so for c should I re-arange the equation like this? :

http://i14.photobucket.com/albums/a315/chibi_lenne/formula.jpg

[arildno]

Alright...so for c should I re-arange the equation like this? :

http://i14.photobucket.com/albums/a315/chibi_lenne/formula.jpg
Why do you think this is a correct manipulation?
Arguments, please.