Question 1071216
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Reena rode her skateboard to her uncle's house, 12 miles away. A wheel broke just as she arrived, so Reena borrowed 
her uncle's bicycle to return home. Traveling by bicycle, she was able to go twice as fast, and returned home in 2 hours less time 
than it took to go to her uncle's house. How long did it take Reena to get home on the bicycle?
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More short and straightforward solution:


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Let   s = her speed skateboarding to uncle's house
Then 2s = her speed biking home

Let   t = time in hrs to skateboard to uncle's house
Then  t - 2 = time in hrs to return home by bike

The distance to there d = st.
The distance back     d = 2s*(t-2).

The distance is the same:  st = 2s*(t-2)   --->  cancel the factor s in both sides  --->

t = 2(t-2)  -->  t = 2t - 4  --->  t = 4.

Thus the time skateboarding is 4 hours.

Hence, the time bicycling is 4 - 2 = 2 hours.
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