Question

$Truck \: is \: moving \: with \: a \\ speed \: of \: 15 m/s . \: A \: car \\ chasing \: this \: truck \: with \: a \\ speed \: of \: 10 m/ s \: fires \: a \: bullet \\ a \: truck \: with \: muzzle \: velocity \\ 90 km / h. \: The \: speed \: with \: which \\ the \: bullet \: hit \: the \: truck \: is : \\ (1) 15 m/s \\ (2) 20 m/s \\ (3) 25m/s \\ (4) 30 m/sec$

Answer 1

Speed of truck = 15 m/s
Speed of bullet = 90 km/hr
90*5/18 = 25 m/s
Speed of car = 10 m/s

Speed of bullet with stationary ground = 10 + 25 - 15
= 35 -15
= 20 m/s

Hope it helps you.

Answer 2

speed of truck=15 m/s

speed of car=10m/s

speed of bullet= 90 km/h x 5/18=25m/s

speed of the bullet with respect to a stationary point on ground

= (speed of car+ speed of bullet)-speed of truck

=10+25-15=20 m/s