SOLUTION: John travelled 30 minutes going 40mph and then slowed down to 20 mph for the remaining 20 minutes. WHat was his average speed in the journey?

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Question 885238: John travelled 30 minutes going 40mph and then slowed down to 20 mph for the remaining 20 minutes. WHat was his average speed in the journey?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Average speed always equals
( total distance traveled ) / ( total time spent traveling )
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Given:
Total time = +30+%2B+20+=+50+ min
In hours:
Total time = +50%2F60+=+5%2F6+ hrs
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For 1st part of trip:
+d%5B1%5D+=+40%2A%281%2F2%29+ ( 30 min = 1/2 hr )
+d%5B1%5D+=+20+ mi
For 2nd part of trip:
+d%5B2%5D+=+20%2A%281%2F3%29+ ( 20 min = 1/3 hr )
+d%5B2%5D+=+20%2F3+ mi
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Average speed = +%28%28+d%5B1%5D+%2B+d%5B2%5D+%29%29+%2F+%28+5%2F6+%29+
Average speed = +%28%28+20+%2B+20%2F3+%29%29+%2F+%28+5%2F6+%29+
Average speed = +%28+80%2F3+%29%2A%28+6%2F5+%29+
Average speed = +160%2F5+=+32+
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His average speed was 32 mi/hr

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