Answer:
10.0 m/s
Step-by-step explanation:
The boy is moving with uniform accelerated motion, so we can use the following suvat equation:
v = u + at
where
v is the velocity at time t
u is the initial velocity
a is the acceleration
For the boy in the problem,
u = 3.0 m/s

Substituting t = 5.0 s, we find the velocity of the boy at that time:
