If he reaches 14 seconds, how far did he travel the tenth second?

Question

A boy in a bicycle coasts downhill, covering 4meters the first second, 12 meters the second second, and in general 8meters more each second than the previous second. If he reaches the bottom at the end of 14 seconds, how far did he travel the tenth second?

Answer 1

speed=4+8*(t-1)

distans=integral(speed)=4t+[8*(t-1)^2 /2]...4t+4*(t-1)^2

at t=14, distans=4*14 +4*(13)^2

=56+4*167

=56+676

=732