B. Solve 1. A bus covers a distance of 90 km at a uniform speed. Had the speed been 15 km/hour more it
would have taken 30 minutes less for the journey. Find the original speed of the bus.

45 km/hr

Explanation:

total distance = 90

Increased speed = x+15

90/x - 90/x+15=1/2

90(1/x - 1/x+15)=1/2

90(x+15-x/x^2+15x)=1/2

equation is:

x^2+15x-2700=0

x^2+60x-45x-2700=0

x(x+60)-45(x+60)=0

(x+60)(x-45)=0

x= -60, x=45

reject the negative value = -60

usual speed=45 km/ hr

because the early people found out about it.