Question 1127041
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<pre>
Her speed downstream is 20 + 5 = 25 km/h.

She spent  {{{1/25}}} of an hour traveling 1 kilometer downstream.



Her speed upstream is 20 - 5 = 15 km/h.

She spent  {{{1/15}}} of an hour traveling 1 kilometer for the returning trip upstream.



In all, she spent  {{{1/25}}} + {{{1/15}}} hours = {{{3/75 + 5/75}}} = {{{8/75}}} hours.



The average rate is the total distance, which is 1 + 1 = 2 kilometers, divided by the total time, which is  {{{8/25}}} hours:


    the average rate = {{{2/((8/75))}}} = {{{(2*75)/8}}} = {{{75/4}}} = 18.75 kilometers per hour.    <U>ANSWER</U>
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Solved.