Explanation : Quantity - I Let speed of the Boat = x Speed of the stream = 3 km/hr
30
x−3
+
30
x+3
=
175
60
60x
x2−9
=
35
12
7x2 – 144x – 63 = 0 7x2 – 147x + 3x –63 = 0 ∴ x = 21 Quantity - II Bus stops = 8 Distance between bus stops = 1 km Total distance = 1 × 7 = 7 km Let speed of car = x Time = 20 min