Question 134208
A bike and a car leave the same house at 9am. The bike goes 20 mph and car goes 50 mph. The both head north. What time is it when they are 126 miles apart?
I think I can figure this out in my head but not algebraically. So each hr the two movers are 30 more miles apart. So in 4 hrs they are 120 miles apart. The remaining 6 miles would be covered in 1/5 of an hour which is 12 minutes. From 9am 4 hrs and 12 minutes gives you a time of 1:12. Is this correct and is there a better algebraic way to figure it out?
:
Here's one way:
Let t = time in hrs when they will be 126 mi apart
:
Write a distance equation: Dist = speed * time
:
Car dist - bike dist = 126 mi
50t - 20t = 126
30t = 126
t = 126/30
t = 4.2 hrs which is 4 hrs and 12 min like you got