a. Velocity = 55 × 3 = 165 ms-1
b. The acceleration is a constant 55 ms-2, so at t = 3 s, the acceleration will be 55 ms-2.
c. The distance travelled in 3 seconds is 165 × 1.5 = 247.5 m. We obtain this from the area under the line between 0 and 3 (i.e. the area of the triangle).
d. The graph: