(Given g = 10 ms-2 and speed of sound = 340 ms-1)
Height = 750m
h = ut + 0.5 gt2
The initial velocity is 0 750 = 0.5 × 10 × t2
t = 10 sec
Speed of sound is 340m/sec
So, time taken to travel 750m upwards is,
\(\frac{750}{340}\) = 2.20 S
time taken = 10 + 2.20 = 12.2 sec.