View Full Version : Quadratic function-word problems
anne21
Oct 28, 2007, 06:12 PM
Car A leaves Toronto for Montreal, 500km away, at an average speed of 80km/h. Car B leaves Montreal for Toronto on the same highway 2h later at 100 km/h. How far are they from Toronto when they pass?
I need a quadratic equation for this please.. tnx in advance. =D
galactus
Oct 29, 2007, 02:42 PM
Use d=rt. Then we have t=d/r.
Car A travels for d/80 hours and car B travels for (500-d)/100 hours.
Their difference is 2 hours.
\frac{d}{80}-\frac{500-d}{100}=2
Solve for d.
Another way to look at it is in terms of distance in terms of time:
car B travels 100(t-2) miles.
100(t-2)=500-80t
Solve for t, the amount of time driven. Then this can be plugged back in to find miles from Toronto.
terryg752
Oct 29, 2007, 08:48 PM
Car A leaves Toronto for Montreal, 500km away, at an average speed of 80km/h. Car B leaves Montreal for Toronto on the same highway 2h later at 100 km/h. How far are they from Toronto when they pass?
i need a quadratic equation for this please.. tnx in advance. =D
AN INTERESTING PROBLEM, IN THE SENSE THAT QUADRATIC EQUATION IS REALLY NOT NECESSARY!
Lets suppose they pass t hours after B starts
So B travels 100t
And A travels (t + 2) 80
Distance from Toronto:
500 - 100t = (t + 2) 80
You can find t from above
distance from toronto: 500 - 100t or (t +2) 80
math122
Oct 12, 2011, 03:53 PM
h(t)=354-5t2+47t