Question 985002

An automobile can travel 200 kilometers in the same time that a truck can travel 150 kilometers. If an automobile travels at a speed of 15 kph faster than the truck, what is the speed of the automobile?
<pre>Let auto's speed be S
Then truck's speed is: S - 15
Time auto takes to travel 200 km: {{{200/S}}}
Time truck takes to travel 150 km: {{{150/(S - 15)}}}
Since times are the same, we get:
{{{200/S = 150/(S - 15)}}}
200(S - 15) = 150S ----- Cross-multiplying
200S - 3,000 = 150S
200S - 150S - 3,000
50S = 3,000
S, or auto's speed = {{{3000/50}}}, or {{{highlight_green(60)}}} km/h