A jogging park has two identical circular tracks touching each other, and a
rectangular track enclosing the two circles. The edges of the rectangles are
tangential to the circles. Two friends, A and B, start jogging simultaneously from the
point where one of the circular tracks touches the smaller side of the rectangular
track. A jog along the rectangular track, while B jogs along the two circular tracks in
a figure of eight. Approximately, how much faster than A does B have to run, so that
they take the same time to return to their starting point?
Ans: 4.72%
Geometry
This topic has expert replies
Since they both take same time to reach their starting point , the ratio of their speeds will be ratio of the distance travelled.
Distance travelled by A = 12R (perimeter of rectangle.)
Distance travelled by B = 4 π R
Speeds of A : Speed of B = 12R:4Ï€R = > 3:Ï€
The question asks Approximately, how much faster than A does B have to run, so that
they take the same time to return to their starting point
(Ï€-3)/3 * 100.
Distance travelled by A = 12R (perimeter of rectangle.)
Distance travelled by B = 4 π R
Speeds of A : Speed of B = 12R:4Ï€R = > 3:Ï€
The question asks Approximately, how much faster than A does B have to run, so that
they take the same time to return to their starting point
(Ï€-3)/3 * 100.
I followed a similar concept, but used numbers to make my math easier, instead of straight algebra.
Lets use easy numbers:
Length of rectangle = 8 (Since, this will give each circle a diameter of 4 and radius of 2. Nice whole numbers)
Since the diameter is 4, the width of the rectangle has to be 4
Permiter of rectangle = 8 + 8 + 4 + 4 = 24
Circumfrence of a circle = 2(3.14)(2) = 12.56
Circumfrence of both circles = 25.12
24 is 96% of 25.
That means the person running on the circles has to walk little faster than 4% of the pace of the person running on the rectangle.
Lets use easy numbers:
Length of rectangle = 8 (Since, this will give each circle a diameter of 4 and radius of 2. Nice whole numbers)
Since the diameter is 4, the width of the rectangle has to be 4
Permiter of rectangle = 8 + 8 + 4 + 4 = 24
Circumfrence of a circle = 2(3.14)(2) = 12.56
Circumfrence of both circles = 25.12
24 is 96% of 25.
That means the person running on the circles has to walk little faster than 4% of the pace of the person running on the rectangle.