English Deutsch Français Italiano Español Português 繁體中文 Bahasa Indonesia Tiếng Việt ภาษาไทย
All categories

First you drive 10 miles at 60 MPH then you drive another 10 miles at 40 MPH. What is your average speed for the trip?
A) 40
B) 48
C) 50
D) 60

Think carefully!

2006-10-04 14:36:06 · 13 answers · asked by Anonymous in Science & Mathematics Mathematics

13 answers

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 · answer #1 · answered by bob h 3 · 0 0

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 · answer #2 · answered by Keith 1 · 0 0

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 · answer #3 · answered by mom 7 · 0 0

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 · answer #4 · answered by Anonymous · 0 0

(60 + 40)/2 = 100/2 = 50

2006-10-04 15:36:01 · answer #5 · answered by Sherman81 6 · 0 1

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 · answer #6 · answered by substanceandevidence 2 · 1 0

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 · answer #7 · answered by frank 7 · 0 1

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 · answer #8 · answered by unmovingasp 3 · 0 1

c) 50

2006-10-04 14:43:07 · answer #9 · answered by First L 1 · 0 1

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 · answer #10 · answered by Anonymous · 0 0

fedest.com, questions and answers