A question asks to calculate "How long the ball was in the air" and provides following data points: $$ initial\ velocity\ \ v_0=10ms^{-1}\\ Angle\ of\ Launch\ = 45^\text{o}\\ Horizontal\ distance \ travelled = 15m$$
The time of flight formula does not utilize range and yields: $$\frac{2*v_y}{g}=\frac{2*10*sin 45^\text{o}}{9.8} = 1.4s$$
While I completely understand the above formulae and reasoning however since the horizontal component has constant velocity I calculated in below manner: $$v_x*t=Range=> 10*cos 45^\text{o}=15=>t=2.12s$$
Is the question incorrect or I am missing something?