Combining Newton's Laws and Kinematic

[gungo]

Homework Statement

Max (65 kg) pushes Toni (50 kg) with a force of 360 N. The force of friction is 0 on Toni and 80 on Max.
(a) Find each girls acceleration
(b) If Max pushes Toni for 0.1 s, how far will Toni travel in 0.5 s?

Homework Equations

Fnet=ma
v2=v1+at
d=v1(t)+1/2a(t)^2

The Attempt at a Solution

For (a), I got the correct answers by using Fnet=ma
Max's acceleration:4.3m/s^2 (left)
Toni's acceleration: 7.2m/s^2 (right)
For (b), Toni's acceleration is only 7.2 during the 0.1 seconds so...
d=v1(t)+1/2a(t)^2
d=(0)(0.1)+1/2(7.2)(0.1)^2
d=0.036
To find the distance for the remaining 0.4 seconds, I need to find v1 which is v2 of the 0.1 seconds
v2=v1+at
v2=7.2(0.1)
v2=0.72 m/s
So v1 for the 0.4 s is 0.72. I assumed acceleration is 0 during this time and that she is now moving at a constant velocity
d=0.72(0.4)+1/2(0)(0.4)^2
d=0.288
d1+d2=0.324
It's very close to the answer my teacher gave which is 0.33 m..but I'm just curious as to why it's a little off because it might be considered wrong on a test.

 

[kuruman]

It's off probably because of round off errors. Carry the intermediate calculations to more decimal places and see what happens. Better yet, derive a symbolic answer and substitute the given quantities at the very end.

On edit: I ran the numbers and got 0.324 m. If you are concerned about this, you may consider asking your teacher.