since h.t is the total time the athlete is in the air, t/2 is the time taken for ascent or descent (t/2 + t/2 = t)
perhaps the initial jump vertical velocity u achieved is from the equation t/2 = u/g
therefore u = 9.8 (1.11/2) = 5.439 m/s
height = u²/2g = 5.439² / 19.6 = 1.5093225 m
Ans: 1.509 m correct to iv s.f
Hope this helps!
Happy Learning!