There is a distance. A person covers it at a speed of 62km/hr. Now, what should be his/her speed of the return journey ( covering same distance at returning), so that he/she can maintain an average speed of 124km/hr of his/her whole journey ?
2007-02-27 02:44:10 · 14 answers · asked by cacher 1 in Science & Mathematics ➔ Mathematics
If we take d to be the distance of the journey in kilometers, then the amount of time it took to go d km on the initial trip is (d/62)hours. (you can use some examples to convince yourself of this, but distance divided by the ratio of distance over time will get you the time taken).
In order to be able to average 124 km/hr for the entire trip (which is 2d km), one would need to complete the entire trip in (2d/124) hours. However, this simplifies to (d/62). In other words, you used up all your alloted time on the first leg of the trip. You'd need to go an infinite speed on the return trip which is impossible so that average couldn't be maintained.
2007-02-27 02:55:44 · answer #1 · answered by Kyrix 6 · 0⤊ 0⤋
Hi.
Let us say that he covers a distance of X. Thus, the total time for the journey (forward and back is)
total T = 2X/124 or X/62
But the problem is the time he spent going forward is
forward T = X/62
Thus,
back T = total T - forward T or back T = X/62 - X/62 = 0
That means, he has consumed all the time he has just for the forward journey. If you want to get technical, he has to travel on the return journey with a speed of
s = X/back T or s = X/0 or s = infinity (otherwise, undefined)
So, he has to travel infinitely fast in the return journey.
2007-02-27 10:58:51 · answer #2 · answered by Moja1981 5 · 2⤊ 0⤋
The average speed for the return journey can never be double that for the outward journey. Average speed is total distance divided by total time.
The answer of 186km/hr is wrong. For this to yield an average speed of 124km/hr, you would have to travel at 186km/hr for the same length of time as the outward journey took, not for the same distance.
2007-02-27 19:07:02 · answer #3 · answered by Anonymous · 0⤊ 0⤋
Let's just assume the person covers 62 km in 1 hour. If he/she returns the total trip will be 124 km. Even if it only takes 0.001 hour to return his/her average speed ( 124km/1.001hr) will be less than 124km/hr. You can easily see from this example that no matter how fast he/she returns, he/she can never reach his/her desired average speed.
As others have said, all of the time has been used up on the initial leg of the journey.
2007-02-27 11:19:55 · answer #4 · answered by indyacom 3 · 1⤊ 0⤋
I'm not sure what you are asking, but if they travel back at twice the speed they went at over the same distance it will take them 1/2 of the time coming back than going.
2007-02-27 10:48:25 · answer #5 · answered by Doctor Q 6 · 0⤊ 0⤋
The total time is coming equal to the time taken for half of the journey.And because i have never dealt with such a question before i satisfy myself by concluding that there is an error in the question itself.
But if the question is correct and has a sensible answer please let me know of it.
2007-02-28 12:12:34 · answer #6 · answered by Nayan 2 · 0⤊ 0⤋
LET THE SPEED BE x
FOR CONVENIENCE LET US ASSUME THE DISTANCE TO BE 62x.
THEN TIME TAKEN TO GO=62x/62=x sec
TIME TAKEN TO RETURN=62x/x=62 sec
AVERAGE SPEED=TOTAL DISTANCE/TOTAL TIME
124=124x/(x+62)
124x-124x=62*124
0x=62*124
x=62*124/0
x=infinite
therefore the speed is infinite
2007-02-27 10:57:58 · answer #7 · answered by satwik 2 · 0⤊ 1⤋
186 km / hr.
Because, average speed = (forward speed + return speed) / 2 = 124 km /hr
FS = 62 km / hr
62 + RS = 124
RS = 124 + 62
RS = 186 km / hr
2007-02-27 10:54:17 · answer #8 · answered by Anonymous · 0⤊ 3⤋
data insufficiency question... data incomplete... u hv 2 provide the distance or the time he took in forward journey...
2007-02-27 10:49:57 · answer #9 · answered by karishma 3 · 0⤊ 2⤋
186km/hr
2007-02-28 03:06:13 · answer #10 · answered by vishwas s 1 · 0⤊ 1⤋