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

let the speed during his first journey be x

and during first journey and later journey be t1 and t2 respectively.

we know that
time = distance / speed

so,
t1 = 50/x
and
t2 = 300/3x. (since it is given that on a later trip he goes three times as fast)

now lets compare new time to the old time.

t1/t2 = (50/x)/(300/3x)
t1/t2 = (50*3x)/(x*300)
t1/t2 = 150x/300x
t1/t2 = 1/2
so,
2*t1 = t2
so the time in second trip was twice the time in first trip.
:-)

Answer 2

Explanation:

Let

• speed of the 1st trip = x miles/hr and
• speed of the 2nd trip = 3x/hr

We know that

Speed = $\frac{ Distance }{ Time }$

OR

Time = $\frac{ Distance }{ Speed }$

So,

=> time taken to covered a distance of 50 miles on his first trip = 50/x hr.

And

=> time taken to covered a distance of 300 miles on his later trip = 300/3x hr.

• 100/x hr

So,

We can clearly see that his new time compared with the old time was : twice as much.