A car speeds up uniformly from rest so that it has a velocity of 30ms -1 after 20 second.How far does the car travel in first 10 seconds?

If car is accelerating uniformly, after 10 seconds, the velocity is 30/2=15 m/s.

Distance travelled is time * average velocity
=10 s × (0+15)/2
= 75 m

Or
calculate average acceleration
a=30 m/s / 20 s
=1.5 m/s²
Distance
=vi t + (1/2) a t²
=0(10)+(1/2)(1.5)(10²)
=0+75
=75 m