<PRE><B>Question 3379</B>
To solve this problem, you need to state it mathematically. First, state the facts:&lt;br&gt;
&lt;ol&gt;
&lt;li&gt;The distance from Denver to LA is 850 miles&lt;/li&gt;
&lt;li&gt;The plane from Denver to LA flies at 410 mph&lt;/li&gt;
&lt;li&gt;The plane from LA to Denver flies at 530 mph&lt;/li&gt;
&lt;li&gt;The plane from LA starts {{{1/2}}} hour earlier&lt;/li&gt;
&lt;/ol&gt;
Now let&#39;s restate these mathematically:&lt;br&gt;
&lt;ol&gt;
&lt;li&gt;Lst t be the time the second plane has been flying, in other words, the first plane took of {{{t - 1/2}}} hours ago&lt;/li&gt;
&lt;li&gt;D = 850 miles, where D is the distance from LA to Denver&lt;/li&gt;
&lt;li&gt;the distance travelled by plane from Denver to LA is 410t&lt;/li&gt;
&lt;li&gt;the distance travelled by plane from LA to Denver is 530t&lt;/li&gt;
&lt;li&gt;the distance the first travelled before the second plane took off is {{{1/2 * 410 = 205}}} miles, so the distance between them at time t is 850 - 205 = 645 miles&lt;/li&gt;
&lt;/ol&gt;
The planes meet when the distances they travelled adds up to 645 (the distance they were from each other at time t). Using the expressions for distance above, this gives us the equation {{{410t + 530t = 645}}} or {{{940t = 645}}}. The time at which the planes meet up is {{{t = 645/940 ~ 0.6862}}}. The distance from Denver travelled by the first plane is {{{205 + 410 *0.6862 = 486.3}}}. The distance travelled by the first plane is {{{530*0.6862 = 383.7}}} miles from LA. This is {{{850 - 383.7 = 486.3}}} miles from Denver. They passed each other 486.3 miles from Denver.</PRE>