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tankabanditka [31]
3 years ago
12

A boat covers 25 km upstream and 44 km downstream in t hours. Also, it covers 15 km upstream and 22 km downstream in 5 hours. Fi

nd the speed of the boat in still water and that of the stream.​
Mathematics
2 answers:
aniked [119]3 years ago
7 0

9514 1404 393

Answer:

  boat speed: (7t -95)/(6t² -110t +500)

  stream speed: (37t -345)/(6t² -110t +500)

Step-by-step explanation:

The relation between time, speed, and distance is ...

  time = distance/speed

The boat speed (b) is added to the stream speed (s) going downstream. The stream speed is subtracted going upstream. The given relations tell us ...

  25/(b-s) +44/(b+s) = t

  15/(b-s) +22/(b+s) = 5

This gives us 2 equations in 3 unknowns, so we can only provide a solution in terms of one of the unknowns. Since we are asked for the speeds, they will be provided in terms of t.

Subtracting the first equation from 2 times the second gives ...

  2(15/(b-s) +22/(b+s)) -(25/(b-s) +44/(b+s)) = 2(5) -(t)

  5/(b-s) = 10 -t

  5/(10 -t) = b -s

Substituting for b-s in the second equation gives ...

  15/(5/(10-t)) +22/(b+s) = 5

  30 -3t +22/(b+s) = 5

  22/(b+s) = 3t -25

  22/(3t -25) = b+s

Adding the equations for the sum and difference of speeds, we get ...

  (b-s) +(b+s) = 5/(10-t) +22/(3t -25)

  2b = (5(3t -25) +22(10 -t))/((10-t)(3t-25)) = (95 -7t)/((10-t)(3t-25))

  b = (7t -95)/(6t² -110t +500)

Subtracting the equations for sum and difference of speeds, we get ...

  (b+s) -(b-s) = 22/(3t -25) -5/(10 -t)

  2s = (22(10-t) -5(3t -25))/((10-t)(3t-25))

 s = (37t -345)/(6t² -110t +500)

__

The speed of the boat in still water is (7t -95)/(6t² -110t +500) km/h.

The speed of the stream is (37t -345)/(6t² -110t +500) km/h.

__

Note that these solutions only make sense for values of t between 25/3 and 345/37, approximately 8.33 < t < 9.32. For t=9 hours, the boat speed is 8 km/h and the stream speed is 3 km/h.

Liula [17]3 years ago
5 0

<h2>Speed of boat in still water</h2><h2>=8km/hr </h2><h2>Speed of stream=3km/hr</h2>

Step-by-step explanation:

Speed of boat in still water=x km/hr

Speed of stream=y km/hr Speed of upstream=x-y km/hr

Speed of downstream=x+y km/hr

Let 1/(x-y)=a and 1/(x+y)=b

Time to go 25km up and 44 down=9

25a+44b=9----->(1)

Time to go 15km up and 22km down=5

15a+22b=5------>(2)

(2) x 2=> 30a+4463D10- ->(3)

(3)-(1)=>5a=1

a=1/5

1/(x-y)=1/5

x-y=5--->(4)

Putting a=1/5 in (1),

5+44b=9

44b=4

b=1/11

1/(x+y)=1/11

x+y=11---->(5)

(4)+(5)=>2x=16

<h2>x=8</h2>

<h2>y=3</h2>
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