Pranali and Prasad started walking to the East and to the North respectively, from the same point and at the same speed. After 2 hours distance between them was 15√2 km. Find their speed per hour.

Distance between Pranali and Prasad after 2 hours = 15√2 km
Since they travel at same speed, they have covered same distance.
Construction: Draw a triangle PQR such that PQ = PR = x and QR = 15√2
P = 90˚
In PQR , PQ²+PR² = QR² [Pythagoras theorem]
x²+x² = (15√2)²
2x² = 2×225
x² = 225
x = 15
Distance covered by them is 15 km.
Given time = 2 hours
Speed = Distance / time
Speed = 15/2 = 7.5km/hr
Speed of Pranali and Prasad is 7.5km/hr.