SOLUTION: A motorcycle that travels 80km/h starts 45 minutes after a truck. If it overtake the truck in 15 minutes, what is the speed of the truck?

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Question 1143161: A motorcycle that travels 80km/h starts 45 minutes after a truck. If it overtake the truck in 15 minutes, what is the speed of the truck?
Found 2 solutions by josmiceli, MathTherapy:
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +s+ = the speed of the truck in km/hr
Let +d+ = distance in km the motorcycle travels in 15 min
---------------------------------------------------------------
Equation for motorcycle:
(1) +d+=+80%2A%28+15%2F60+%29+
Equation for truck:
(2) +d+-+s%2A%2845%2F60+%29+=+s%2A%28+15%2F60+%29+
----------------------------------------
(1) +d+=+80%2A%28+1%2F4+%29+
(1) +d+=+20+ km
and
(2) +d+-+s%2A%28+3%2F4+%29+=+s%2A%28+1%2F4+%29+
(2) +d+=+s+
(2) +s+=+20+ km/hr
---------------------------------
check answer:
In 45 min plus 15 min, the truck travels distance +d+
+d+=+20%2A1+
+20+=+20+
OK

Answer by MathTherapy(10551) About Me  (Show Source):
You can put this solution on YOUR website!

A motorcycle that travels 80km/h starts 45 minutes after a truck. If it overtake the truck in 15 minutes, what is the speed of the truck?
In 15 mins (¼ hour), and at a speed of 80 km/h, the bike traveled ¼(80), or 20 km

The truck also traveled 20 km, but in (45 + 15) mins, or 1 hour, so: