Find distance traveled using acceleration graph

[denxnis]

Homework Statement

Here is a link to the graph.

http://www.webassign.net/pse/pse6_p2-12.gif

Find the distance traveled in the first 20 seconds.

Homework Equations

Integral once = velocity
Integral twice = position

I attempted to use the following formula:

a = [ 2 ( x - x(sub-i) ) ] / 2

The Attempt at a Solution

When I integrated twice i came up with, 100m however this is incorrect
Then I somehow came up with 137.5, this is incorrect.
I attempted to use the following formula:

a = [ 2 ( x - x(sub-i) ) ] / 2

unfortunately I came up empty handed.

Please help! this problem is killing me.
Thank you for your time.

 

[rl.bhat]

While coming up with 137.5 m, I think, you have left out the distance traveled with uniform velocity during 10 to 15 seconds.