Question 184240
to attend a wedding Barbara starts driving west from Woodstock at 80km/h. One hour later, Barbara's parents leave Woodstock and drive along the same road at 100 km/h. At what distance from Woodstock will Barbara's parents pass her? 
:
let d = distance when this occurs
:
Write a time equation: time = {{{dist/speed}}}
:
B's time = P's time + 1 hr
{{{d/80}}} = {{{d/100}}} + 1
Multiply eq by 400:
400*{{{d/80}}} = 400*{{{d/100}}} + 400(1)
cancel out the denominators
5d = 4d + 400
5d - 4d = 400
d = 400 km from W.
:
:
Check solution, find the travel for each
400/80 = 5 hr
400/100 =4 hr; 1 hr difference