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[juswanthatDDS]

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A boat travels between two cities A and B 21 miles apart. The river flows in direction from a to b at 2 mph. Boat takes 10 hrs for a round trip. How long does it take to take the boat to make a one way trip from a to b if boats speed remains constant to speed of the river in each direction

2hrs
3
4
5
6

I can set it up to 21/x+2 + 21/x-2 = 10
But then what do I do?

 

[tendram]

So you have:

21/(x+2) + 21/(x-2) = 10

Factoring out 21 will give you

1/(x+2) + 1/(x-2) = 10/21

which makes it a little less confusing. In order to add the two you must first find a common denominator which in this case is (x+2)(x-2). Multiplying out and then adding the two together should give you

2x/(x+2)(x-2) = 10/21

Since both numbers on either side of the equals sign are fractions you can say that 2x = 10 and that (x+2)(x-2) = 21. Solving these gives x = 5. After this all you have to do is plug and play and you get that the answer is 3h. Hope that helps 👍

 

[juswanthatDDS]

Thank u!