document.write( "Question 821094: What is the average rate, in miles per hour, of a car that travels 20 miles at 40 miles per hour and then 10 miles at 60 miles per hour?\r
\n" ); document.write( "\n" ); document.write( "I also need a formula to along with this. Thank you! \n" ); document.write( "
Algebra.Com's Answer #493897 by TimothyLamb(4379)\"\" \"About 
You can put this solution on YOUR website!
time per leg:
\n" ); document.write( "t = d / s
\n" ); document.write( "t = 20/40 + 10/60
\n" ); document.write( "t = 1/2 + 1/6
\n" ); document.write( "t = 6/12 + 2/12
\n" ); document.write( "t = 8/12
\n" ); document.write( "---
\n" ); document.write( "avg speed:
\n" ); document.write( "s = d / t
\n" ); document.write( "s = (20 + 10)/(8/12)
\n" ); document.write( "s = (30)/(8/12)
\n" ); document.write( "s = 45 mph
\n" ); document.write( "---
\n" ); document.write( "NOTE:
\n" ); document.write( "avg speed is NOT: (40+60)/2=50
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