How do I do this word problem? (calculus) 10 pts for best answer?

Question

A modern jet fighter aircraft needs to be travelling at 180 yards/sec down the runway in order to take off. It is known that the jet can accelerate from 0 to 180 yards/sec in 10 seconds (assume constant acceleration).

Determine the shortest length the runway can be if the plane starts from rest at one end and has to take off at least 140 yards before the runway ends?

Answer 1

vf^2 = v0^2 + 2as

180^2 =0 + 2(18)s

s=900 yards

So 900 + 140 = 1040 yards  ANSWER

Answer 2

v^2 = u^2 + 2as

180^2 = 0^2 + 2(18)s

32400 = 36s

s = 900 yards + 140 = 1040 yards

Answer 3

1040 { tax time}...average velocity for 1st 10 seconds is 90 yd/sec..thus travels 900 yds, add 140 yds.