Explanation:
in that setup they will both explode after traveling the same distance.
A is just going faster and has to launch therefore a little bit later.
so, we need to make an equation based on distance traveled and find in that process the number of seconds needed to travel that distance.
speed is distance/time, so we need to multiply speed by time to get distance.
x = seconds for B
x - 0.25 = seconds for A
A is launched after B but explodes at the same time.
so, A's trip is of shorter time than B's trip.
(x - 0.25)×360 = x×320
360x - 90 = 320x
40x - 90 = 0
40x = 90
4x = 9
x = 9/4 = 2.25 seconds
both fireworks will explode 2.25 seconds after B launches (and 2.25 - 0.25 = 2 seconds after A launches).
the explosion will be at
320×2.25 = 360×2 = 720 feet height.