Question 909182
Jojomar and his father began biking the same trail at the same time. 
If Jojomar, who averages 9 kph, finished the trail 0.5 hour quicker than his father, who averages 6 kph, find the length of the trail.
:
let d = the length of the trail in km
:
Write a time equation; time = dist/speed
:
Dad's time - Jo's time = .5 hr
{{{d/6}}} - {{{d/9}}} = .5
Multiply equation by 18, the least common multiple of 6 and 9:
18*{{{d/6}}} - 18*{{{d/9}}} = .5(18)
cancel the denominators
3d - 2d = 9
d = 9 km is the length of trail
:
:
see if that checks out, find the actual time of each
9/6 = 1.5 hrs
9/9 = 1.0 hrs
-------------
differ: .5 hrs