Distance between Davien's school and beach, D = 50 km.
Also, Davian's house is 10 km closer to the beach than the school.
So, distance between Davien's house and beach, d = 40 km.
Speed of Davian, s = 40 km/h.
Now, time taken is given by :
Therefore, Davien reach the beach at 1 : 30 P.M .
Hence, this is the required solution.