Allison drove half the distance from Arthur to Bethany at 40 mph and the rest of the trip at 60 mph. What was her average speed for the whole trip? (Remember you can't take the average of averages)
2006-11-02 17:00:44 · 7 answers · asked by Anonymous in Education & Reference ➔ Homework Help
let total distance be x. then first x/2 @ 40kmph and next x/2 @60kmph
total time taken is x/80 +x/120 = 5x/240
total distance is x . so average speed is total distance /total time:
x * 240/(5x) = 240/5 = 48kmph.
hope this helps
( average speed is always total distance/total time)
2006-11-02 17:13:15 · answer #1 · answered by yog 2 · 0⤊ 0⤋
Since the problem states that Alison drove half the distance at 40 mph and not half the time at 40 mph you can't just add and divide.
Let's say that the total distance is 100 miles. That would mean that she drove 50 miles at 40 mph which would take 1.25 hours. The remaining distance of 50 miles would take .83 hours at 60 mph.
Her average speed would be 100 miles divided by 2.08 hours, which equals 48.07 mph.
2006-11-03 01:18:56 · answer #2 · answered by Don E 4 · 0⤊ 0⤋
The answer would be: 50 mph.
It doesn't say that 40 and 60 are averages. Take them as exactly what they say they are.
2006-11-03 01:10:31 · answer #3 · answered by Hemp 2 · 0⤊ 0⤋
40 + 60 = 100
100 x 0.5 = 50mph
multiply by 0.5 since each speed was for half of the trip
2006-11-03 01:13:59 · answer #4 · answered by jeffsgirl 2 · 0⤊ 0⤋
48 mph
2006-11-03 01:13:27 · answer #5 · answered by jerrydba 2 · 0⤊ 0⤋
50mph
add the 60 and the 40 and devide them by 2 thats ur answer.
2006-11-03 06:28:25 · answer #6 · answered by fat_arse 3 · 0⤊ 0⤋
40 + 60
divide by 2
= 50mph
2006-11-03 07:41:02 · answer #7 · answered by ♥♫♥ÇHÅTHÜ®ÏKÃ♥♫♥ 5 · 0⤊ 0⤋