Maths Question, help please (1 Viewer)

[Over97]

yo, im stuck on this question, n e assitance will be most appreciated.


if spliff walks at 1km/h faster than his usual speed, he takes 15 minutes less than usual for a distance of 5km/h.
Letting his usual rate of waling be xkm/h, use algebra to find his usual rate of walking.

the solution in my paper is

1) 5/x - 1/4 = 5/x+1

2) 20-x/4x = 5/x+1

a quadratic is formed, its solved
and we get 4.

i dont understand step 1, can n e 1 please explain this 2 me.

thanks

 

[Lazarus]

note:
s₁, x₁ = usual rate of walking
s₂ = faster rate of walking

t₁ = time for 5km at the usual rate of walking
t₂ = time for 5km at the faster rate of walking

15 minutes is 1/4 of an hour

step one:

distance = speed * time

s₂ = d/t₂

x₁ + 1 = 5/(t₁ - 1/4)

but t₁ = d/s₁

.'. t₁ = 5/x₁

i.e.

x₁ + 1 = 5/((5/x₁) - 1/4)

5/x₁ - 1/4 = 5/(x₁ + 1)