10m/s
- Akash Anand Good Work :)
rate of increasing of the length of shadow dxdt
given,
dydt=7 m/s
velocity of the shadow = dxdt+dydt
AB=5m, MN=1.5m
From ΔABP & ΔMNP
PMMN=PAAB
Or,x1.5=x+y5
or, 7x=3y
or, x=37y
diff. both side w.r.t. t
dxdt=37dydt=3m/s
now, velocity of the shadow = dxdt+dydt=7+3=10 m/s
It will be better if any other people (Not these two who answered already) provide the solution.