A car accelerates from rest with 2m/s² on a straight line path and then comes to rest after applying brakes. Total distance travelled by the car is 100 m in 20 seconds. Then the maximum velocity attained by the car is

Given Acceleration a  = 2 m/s²

Velocity v = $\int adt$= 2t + v₀

Given  V₀ is 0

v= 2t till there is an acceleration. 

V-T graph :

The area under the v-t curve (in this case it is a triangle) is the same as displacement.
1/2​vt = 100

⇒v = 200​/t = 10 m/s