.
Let "w" be her rate walking, in km/h.
Then the biking rate is (w+8) km/h.
From the condition you have this equation
=
saying that the distance is the same in both directions.
From the equation (canceling 60 in the denominators)
25*(w+8) = 75w
w + 8 = 3w
8 = 3w - w = 2w
w = 8/2 = 4 km/h.
So, the walking rate is 4 km/h; then the (walking) distance is
= 5 kilometres. ANSWER
Another solution
Let "d" be the distance under the question.
Then from condition you have this equation, connecting rates
-
=
kilometres per minute.
Simplify by canceling factor 5 in denominators
-
=
=
.
Multiply both sides by 15
3d - d = 10
2d = 10
d = 10/2 = 5 kilometres,
and you get the same answer for the distance.
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Solved two times by different methods for your better understanding.