Brain Teasers
Trip to Pinewood
The drive from Oakland to Pinewood was a tricky one. I covered the uphill distance of 70 miles at 42 miles per hour. The return journey from Pinewood to Oakland was downhill, and I managed to drive at 56 miles per hour. What was my average speed for the entire journey?
Answer
My average speed was 48 miles per hour.Total distance = 2 x 70 miles.
Time for uphill journey (from Oakland to Pinewood) = 70 / 42 hours.
Time for downhill journey (from Pinewood to Oakland) = 70 / 56 hours.
Total time = (70 / 42) + (70 / 56) = 2 x 70 / 48 hours.
Average speed = Total distance / Total time = 48 miles per hour.
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