It's not a race

Algebra Level 2

A car passes point A driving at a constant rate of 60 km/h. A second car, traveling at a constant rate of 75 km/h, passes the same point A a while later and then follows the fist car. It catches the first car after traveling a distance of 75 km past point A . How many minutes after the first car passed point A did the second car pass point A ?


The answer is 15.

Finn Hulse by Finn Hulse , 21, USA

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3 solutions

Omkar Pande
Feb 14, 2014

Time taken by 1st car to travel 75 km = (75/60) hrs. = 1.25 hrs.

Time taken by 2nd car to travel 75 km = (75/75) hrs. = 1 hr.

1.25 hrs. - 1 hr. = 0.25 hrs. = 15 minutes

5 Helpful 0 Interesting 0 Brilliant 0 Confused

Ugh, hadn't even known you could just do that. I was sitting on my couch for literally 30 minutes trying to figure that question out.

Robert Fritz - 7 years, 2 months ago

I liked this question. Do I need a Solid reason? No. Why? Because I have rights.

Robert Fritz - 7 years, 2 months ago

Awesome!

Finn Hulse - 7 years, 3 months ago

what a simple answer dude

ashutosh mahapatra - 7 years, 2 months ago

a fan of sherlock or what

ashutosh mahapatra - 7 years, 2 months ago
Robert Fritz
Feb 16, 2014

First you need to figure out how far "A" is. To do this, since car 2 catches car 1 75 km after "A". "A" is the LCM of 75 and 60-75 which is 225. Then I figured out the time each car took to move the total distance which is 300/60=5, and 300/75=4. Then, that means that car 1 got a 1 hr head start. Since it takes 45 minutes longer without a head start for car 1 to get to A 60-45=15 minutes.

2 Helpful 0 Interesting 0 Brilliant 0 Confused

Pretty good! Hadn't thought of it like that really.

Finn Hulse - 7 years, 3 months ago

i think this made me confused. haha

Oy Ie - 7 years, 3 months ago
Mary Tan
Mar 30, 2014

The second car traveled the 75 km for an hour while the first car traveled the 75km in 1hour +x. By using the formula d=st, we can find that x = 15minutes. Since x is the number of minutes that the first car traveled after passing the point A before the second car passes it, 15 minutes is the answer.:)

0 Helpful 0 Interesting 0 Brilliant 0 Confused

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