### 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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## Comments

two variables - 42 & 56 (70 is a constant and can be ruled out)

42+56=98

98/2=49 MPH

42+56=98

98/2=49 MPH

This is the only reason I don't allow my kids to access the internet for their homework - people like you.

What do yo mean, Yogi?

Sorry, Yogi - the answer given is right. You can't just average the two speeds because more time is spent travelling at the slower speed, so it carries more weight. Think of it this way: If I travel 60 mph for 1 mile (taking 1 minute) and then 1 mph for 1 mile (taking 1 hour), according to you my average speed would be 30.5 miles per hour. If you travel 30.5 miles per hour will it take you over an hour to travel 2 miles? Don't think so. By the way, I think you owe Cas an apology - "People like him" (or her) apparently know a little more than "people like you."

lets just hope that Yogi never helps his kids with their homework!

I'd say Yogi made a Boo-Boo!

I dont get why not 49 mph

Oh, never mind, get it now.

Oh, never mind, get it now.

I think you ment hours and not mph because the mileage doesn't matter if your doing 42 oneway and 56 the other the average is 49mph

I think you all owe Yogi an apology

please how was 48 gotten can't figure that out

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