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you, in your new red Porsche, decide to make a 160km trip to Carolina Beach, traveling at 80km?hr. Your make a return trip at a rate of 48km?hr. What was your average speed for the entire trip?
 one year ago
 one year ago
you, in your new red Porsche, decide to make a 160km trip to Carolina Beach, traveling at 80km?hr. Your make a return trip at a rate of 48km?hr. What was your average speed for the entire trip?
 one year ago
 one year ago

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satellite73Best ResponseYou've already chosen the best response.0
figure out the total time, and the total distance divide the total distance by the total time
 one year ago

satellite73Best ResponseYou've already chosen the best response.0
ok it was easy but i got it wrong total distance is \(2\times 160=320\)
 one year ago

satellite73Best ResponseYou've already chosen the best response.0
time going in your new red porche is \(\frac{160}{80}=2\)
 one year ago

satellite73Best ResponseYou've already chosen the best response.0
how about the time returning?
 one year ago

jdlandrethBest ResponseYou've already chosen the best response.0
ugh i don't know cause it comes out as a decimal?
 one year ago

satellite73Best ResponseYou've already chosen the best response.0
much easier (believe it or not) if you leave it as a fraction
 one year ago

satellite73Best ResponseYou've already chosen the best response.0
in other words, take \(\frac{160}{48}\) and instead of writing it as a repeating decimal, reduce it to \(\frac{10}{3}\)
 one year ago

jdlandrethBest ResponseYou've already chosen the best response.0
okay so? then do i leave the other as 2? or 160/2?
 one year ago

satellite73Best ResponseYou've already chosen the best response.0
now the next job is to total up the time, in other words compute \[2+\frac{10}{3}\] leave it as a fraction
 one year ago

satellite73Best ResponseYou've already chosen the best response.0
right and now speed is distance divided by rate
 one year ago

satellite73Best ResponseYou've already chosen the best response.0
so your final job is \[320\div \frac{16}{3}\]
 one year ago

jdlandrethBest ResponseYou've already chosen the best response.0
So the average is 60?
 one year ago

satellite73Best ResponseYou've already chosen the best response.0
that is what i get too
 one year ago

jdlandrethBest ResponseYou've already chosen the best response.0
kay good. Thank you!!
 one year ago

satellite73Best ResponseYou've already chosen the best response.0
notice two things 1) the average speed is not the "average of the speeds" and 2) the 160 is a red herring if you really want to impress your math teacher, show that it works no matter how far you drive
 one year ago

satellite73Best ResponseYou've already chosen the best response.0
you could drive 160 miles or 100 miles or 3,000 miles or \(m\) miles, the average will still be 60
 one year ago

jdlandrethBest ResponseYou've already chosen the best response.0
Okay Thank you soo much. =)
 one year ago

satellite73Best ResponseYou've already chosen the best response.0
try it with \(m\) you get \[\frac{2m}{\frac{m}{80}+\frac{m}{48}}=60\] after some algebra
 one year ago
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