A) (x+y+z)/3
B) (3xyz)/(xy+yz+zx)
C) (xyz)/(x+y+z)
D) (xy+yz+zx)/(x+y+z)
E) [3(x+y+z)]/(xyz)
[spoiler]Ans: B[/spoiler]
This is a tough one... GMAT experts want to give this one a try?
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benjiboo wrote:Jacob drove from Town A to Town B at an average rate of x miles per hour, then returned along the same route at y miles per hour. If he then drove back to Town B at z miles per hour along the same route, what was Jacob's average rate of speed for the entire trip, in miles per hour?
A) (x+y+z)/3
B) (3xyz)/(xy+yz+zx)
C) (xyz)/(x+y+z)
D) (xy+yz+zx)/(x+y+z)
E) [3(x+y+z)]/(xyz)
[spoiler]Ans: B[/spoiler]
This is a tough one... GMAT experts want to give this one a try?
Let the distance = 12 miles.benjiboo wrote:Jacob drove from Town A to Town B at an average rate of x miles per hour, then returned along the same route at y miles per hour. If he then drove back to Town B at z miles per hour along the same route, what was Jacob's average rate of speed for the entire trip, in miles per hour?
A) (x+y+z)/3
B) (3xyz)/(xy+yz+zx)
C) (xyz)/(x+y+z)
D) (xy+yz+zx)/(x+y+z)
E) [3(x+y+z)]/(xyz)
[spoiler]Ans: B[/spoiler]
This is a tough one... GMAT experts want to give this one a try?
Average speed = (total distance traveled)/(total travel time)benjiboo wrote:Jacob drove from Town A to Town B at an average rate of x miles per hour, then returned along the same route at y miles per hour. If he then drove back to Town B at z miles per hour along the same route, what was Jacob's average rate of speed for the entire trip, in miles per hour?
A) (x+y+z)/3
B) (3xyz)/(xy+yz+zx)
C) (xyz)/(x+y+z)
D) (xy+yz+zx)/(x+y+z)
E) [3(x+y+z)]/(xyz)
To make the algebra easier, let the distance in each direction = 1.benjiboo wrote:Jacob drove from Town A to Town B at an average rate of x miles per hour, then returned along the same route at y miles per hour. If he then drove back to Town B at z miles per hour along the same route, what was Jacob's average rate of speed for the entire trip, in miles per hour?
A) (x+y+z)/3
B) (3xyz)/(xy+yz+zx)
C) (xyz)/(x+y+z)
D) (xy+yz+zx)/(x+y+z)
E) [3(x+y+z)]/(xyz)
Hi benjiboo,benjiboo wrote:Jacob drove from Town A to Town B at an average rate of x miles per hour, then returned along the same route at y miles per hour. If he then drove back to Town B at z miles per hour along the same route, what was Jacob's average rate of speed for the entire trip, in miles per hour?
A) (x+y+z)/3
B) (3xyz)/(xy+yz+zx)
C) (xyz)/(x+y+z)
D) (xy+yz+zx)/(x+y+z)
E) [3(x+y+z)]/(xyz)
[spoiler]Ans: B[/spoiler]
This is a tough one... GMAT experts want to give this one a try?
Needless to state that the answer would not be the arithmetic mean of 30 and 40 = 35 miles per hour.Let us a see a simple question.
If Jack drives from city A to B at a uniform speed of 30 miles per and returns to A from B at a uniform speed of 40 miles per, what is his average speed for the entire journey?
To solve, we can use the formula for average rate:benjiboo wrote:Jacob drove from Town A to Town B at an average rate of x miles per hour, then returned along the same route at y miles per hour. If he then drove back to Town B at z miles per hour along the same route, what was Jacob's average rate of speed for the entire trip, in miles per hour?
A) (x+y+z)/3
B) (3xyz)/(xy+yz+zx)
C) (xyz)/(x+y+z)
D) (xy+yz+zx)/(x+y+z)
E) [3(x+y+z)]/(xyz)
The denominator goes like so:Zoser wrote:Can you please explain how you get rid of D in the last step?= (d + d + d)/(d/x + d/y + d/z) = (3d)/(dyz + dxz + dyx)/(xyz)
= (3xyz)/(yz + xz + yx)
Thanks