Question 1203619
A passenger plane left Tokyo and flew toward Las Vegas. Two hours later a cargo
plane left flying 70 km/h faster in an effort to catch up to it. After five
hours the cargo plane finally caught up. Find the passenger plane's average
speed.<pre>
Let the passenger plane's average speed be r. Then the cargo plane's average
speed is r+70.

The cargo plane's time is 5 hours. The passenger plane's time is 2 hours more,
or 7 hours.  Rate x Time = Distance.  Their distances are equal when the cargo
plane catches up. 

               |  Rate  |  Time  |Distance|
Passenger plane|    r   |   7    |   7r   |
Cargo plane    |  r+70  |   5    |(r+70)5 |

7r = (r+70)5
7r = 5r+350
2r = 350
 r = 175 km/h

Edwin</pre>