Question

A van travels at a constant speed of x km/hr over a distance of 45km/hr. If the van increases its speed by 4km/h, it will be able to travel a distance of 48km in the same amount of time. Calculate x.

Answer 1

Speed = Distance/Time. Let speed be V, distance D and time T

a)Given: D₁ =45km, V₁=x km/h 
V₁=D₁/T
V₁=45/T OR T= 45/V₁

b) Given : D₂ =48 km and V₂ = V₁ + 4 km/h
V₂ = 48/T, but V₂ = V₁+4, then:

V₁+4 = 48/T OR  T=48/(V₁+4). Since Time is same, then we can write:
45/V₁ =48/(V₁+4), solve for V₁:
45V₁ + 180 = 48V₁

3V₁ =180 and V₁ = x = 60 km/h