Which max the horizontal range are same?

Question

What are the correct pair of launching angles for which the max horizontal ranges are same?

a) 30,60

b) 20,60

c) 40,80

d) 60,70

Answer 1

Range = v² sin (2θ)/ g .

So you need to look at the four pairs of angles and see for which pair sin (2θ) is the same for both angles.