Apyrotechnician plans for two fireworks to explode together at the same height in the air. they travel at speeds shown below. firework b is launched 0.25 s before firework a. how many seconds after firework b launches will both fireworks explode?

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By the time firework a has been launched, firework b has already been launched for 0.25 seconds, so if we treat the two as equations, then

a = 220 (t)
b = 220 (t) +  220 (.25)

And we want to know when these two equal eachother, as that's they will both detonate.

220t = 200 t + 200 (.25)
20t = 50 
t = 2.5