Question

Stardust the unicorn, covered a distance of 50 miles on his first trip to the forest. On a later trip he travelled 300 miles while going three times as fast. His new time compared with the old time was:

Answer 1

Answer: (B) Twice as much

We are going to use the definition of speed:

speed = distance/time

In this first trip, Stardust, covered 50 miles, this is:

s = 50/t, now we are going to express the time:

t₁ = 50/s

In his second trip, Stardust covered 300 miles, but with a triple speed increase (3s):

3s = 300/t, in function of time

t = 300/3s

t₂ = 100/s

We are to compare:

t₁/t₂ = (50/s)/(100/s)

t₁/t₂ = 50s/100s

t₁/t₂ = 1/2

So: t₂ = 2t₁