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## #1 2013-08-23 18:47:31

shivusuja
Member
Registered: 2006-09-14
Posts: 56

### linear equation in two variable

A BOAT CAN TRAVEL15km/hr IN STILL WATER MOVES AT DISTANCE 30KM UPSTREAM AND SAME THE DOWN STREAM IN 4hr 30 min . FIND THE SPEED OF STREAM.

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## #2 2013-08-23 19:07:12

bob bundy
Registered: 2010-06-20
Posts: 8,445

### Re: linear equation in two variable

hi shivusuja

When travelling  downstream the boat will move (relative to the land) at a velocity 15 + v where v is the velocity of the stream.

And upstream at a velocity 15 - v

So you can use

in the two cases using 30 for the distance and v for the velocity of the stream.

Get the time for each, add them and set that equal to 4.5 to find v

Bob

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob Bundy

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## #3 2013-08-23 22:34:10

shivusuja
Member
Registered: 2006-09-14
Posts: 56

### Re: linear equation in two variable

The Sum Is To Be Done In Two Variables[x,y]

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## #4 2013-08-24 06:22:43

bob bundy
Registered: 2010-06-20
Posts: 8,445

### Re: linear equation in two variable

That seems to make the question unnecessarily complicated but OK, you could do this:

Let t be the time for the upstream journey.

Then (4.5 - t)  is the time for the downstream journey.

Now you have two variables, t and v.

Same method, just takes longer, as the first step is to eliminate t.

Bob

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob Bundy

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