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# You can drive at a speed of 65 miles/hour whereas your spouse can drive at a speed of...

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You can drive at a speed of 65 miles/hour whereas your spouse can drive at a speed of 35 meter/second. Who can drive faster? 1km=0.621mile, 1hr=60min

it's general chemistry

Posted by rannia24 on February 1, 2009 at 7:54 PM via web and tagged with math, math problem

High School Teacher

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The easiest way to figure out this type of question without being confused is to use dimensional analysis.  That means when you divide, the units that you don't want will cancel, and what you want will be left.  So,

35 meters/second * 60seconds/minute * 60 minutes/hour = 126000 meters/hour (seconds and minutes cancel).

126000meters/hour * 1km/1000meters * .621 mile/1km = 78.246 miles/hour (meters and kilometers cancel).

So, she drives 78 mph and you drive 65 mph.  She drives faster.

(If you rewrite the calculations as true fractions, it is easier to see what cancels.)

Posted by mcetner on February 7, 2009 at 1:22 AM (Answer #1)

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One hour is 60 minutes and each minutes is 60 seconds.

So, one hour = 60 x 60 seconds = 3600 seconds.

She drives 35 meters in 1 secend.

So in an hour she drives 3600 x 35 = 126,000 meters.

126,000 meters is 126 Kilometers.

1km = 0.621 miles

126 x 0.621 = 78.24 miles

She drives 78.24 miles per hour.

He drives at 65 miles per hour.

She drives faster.

Posted by frizzyperm on February 1, 2009 at 9:02 PM (Answer #2)

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1 km= 1000m, so:

1000m=0.621 miles

35m= 0.021735 miles

1s= 1/3600h

so spouse's speed is 0.021735/1/3600= 78.246 miles/h

My speed is at 65 miles/h, so SPOUSE drives faster than me.

Posted by revolution on September 9, 2010 at 12:16 AM (Answer #3)