Question 31173
Hello!
Let's call X to the speed of the fast car. The time needed for a car going at X miles per hour (mph) to travel 90 miles is:

{{{90/X}}}
[for example, if it were going at 45 mph, it would need 2 hours to travel 90 miles]

The other car travles 10 mph slower; that is, at {{{X-10}}} mph. The time it takes this car to travel 60 miles would then be:

{{{60/(X-10)}}}

But we also know that these times are equal. So we have the equation:

{{{90/X = 60/(X-10)}}}
Cross-multiplying:
{{{90X - 900 = 60X}}}
{{{30X = 900}}}
{{{X = 30}}}

The fast car travels at 30 mph; the other one, at 20 mph.


I hope this helps!

Get more answers at <a href=http://www.onlinemathanswers.com>Online Math Answers.com</a>!