Princeton CAT1 - rate

[gbb]

Princeton CAT1, help!!!

Angela walks along a trail at a rate of 3 kilometers per hour and returns along the same route at a rate of 4 kilometers per hour. If her total walking time is 105 minutes, how long is the trail in kilometers?

A-9
B-8
C-6
D-3
E-1.5

Answer D.

I answered this question backsolving... anyone knows how to solve with algebra?

backsolving...

r*t=d
6km/hr, then 3*t1=6, 2 hours (more than 105mins).
4*t2=6, 3/2 or 1.5hours
total=3h30min - wrong

3km/hr, then 3*t1=3, 1 hour.
4*t2=3, 3/4 or 45 mins.
total=1h45min or 105 minutes

[truplayer256]

Let x represent the distance of the trail that Angela travels.

x/3+x/4=105/60<--- Don't forget to divide the 105 by 60 since Angela is walking in miles per hour.

7x=21
x=3