you have driven 20 miles in
1/6 hr + 1/4 hr = 5/12 hr
in 1 hr you drive 20*12/5 = 48 MPH
2006-10-04 14:43:09
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answer #1
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answered by bob h 3
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To do this problem, you must use the harmonic mean and not the arithmetic mean.
2 / (1 / 60 + 1 / 40) = 48 mph
2006-10-04 14:58:50
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answer #2
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answered by Keith 1
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D=RT
10=60T
1/6 hour or 10 minutes is the time
D=RT
10=40T
1/4hour or 15 minutes is the time
the total time is 25 minutes, or 25/60 of an hour
the total distance is 20 miles
D=RT
20=R(25/60) I reduce the fraction to make it easier
20=R(5/12) Now multiply both sides by 12
240=5R and divide by 5
48=R
The average rate is 48 miles per hour.
2006-10-04 14:49:35
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answer #3
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answered by mom 7
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First segment takes 6 minutes
Second segment takes 15 minutes
Total time is 15 minutes which is 5/12 of an hour.
take 20miles and divide by 5/12 hour and you get 48 miles. End of Story.
2006-10-05 16:01:53
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answer #4
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answered by Anonymous
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(60 + 40)/2 = 100/2 = 50
2006-10-04 15:36:01
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answer #5
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answered by Sherman81 6
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B) 48
Total time traveled: 5/12 hr.
Total distance traveled: 20 mi.
Average Speed = total distance/ total time
20 / (5/12) = 48 mph
2006-10-04 14:46:47
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answer #6
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answered by substanceandevidence 2
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average speed= (first speed + second speed)/2
= (40 mph + 60mph)/2
= 100 mph/2
= 50 mph
Answer: 50mph => C
2006-10-04 14:43:10
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answer #7
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answered by frank 7
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My friend Artwork says "C" but I do not find my answer in the selections....2 different average speeds....60 & 40.
COMMON SENSE!
2006-10-04 14:48:22
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answer #8
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answered by unmovingasp 3
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c) 50
2006-10-04 14:43:07
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answer #9
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answered by First L 1
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x1 = value of automobile on flat floor x2 = value of automobile contained in the mountains r *t = d x1 * t = 4 hundred x2 * t = a hundred and sixty x2 = x1 - 30 4 hundred/x1 = a hundred and sixty/x2 4 hundred*x2 = a hundred and sixty *x1 4 hundred (x1 -30) = a hundred and sixty x1 4 hundred x1 - 12000 = a hundred and sixty x1 240 x1 = 12000 x1 = 50 mph x2 = 20 mph
2016-10-01 22:58:20
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answer #10
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answered by Anonymous
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