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shivusuja

Member

Registered: 2006-09-14

Posts: 56

linear equation in two variable

please help me out with steps

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.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,621

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

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]

Bob

Administrator

Registered: 2010-06-20

Posts: 10,621

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