In this page quadratic equation practical solution6 we are going to see solution of practice question of the worksheet quadratic equation practical application.

**Question 6:**

The speed of a boat in still water is 15 km/hr. It goes 3 km upstream and return downstream to the original point in 4 hrs 30 minutes. Find the speed of the stream.

**Solution:**

Let “x km/hr” be the speed of water

Speed of boat is 15 km/hr

So speed is upstream = (15 + x) km/hr

Speed in downstream = (15 –x) km/hr

Let T1 be the time taken to cover the distance 30 km in upstream

Let T2 be the time taken to cover the distance 30 km in downstream

Time = Distance/Speed

T1 = 30/(15 + x)

T2 = 30/(15 - x)

T1 + T2 = 4 hours 30 minutes

T1 + T2 = 4 ½

[30/(15 + x) + 30/(15 - x)] = 9/2

30[1/(15 + x) + 1/(15 - x)] = 9/2

30 [(15 – x + 15 + x)/(225 - x²)] = 9/2

30 (30)/(225 - x²) = 9/2

900 x 2 = 9 (225 - x²)

Now let us divide the entire equation by 9

So that we will get 200 = (225 - x²)

225 - x² = 200

225 – 200 = x²

x² = 25

x = √25

x = ± 5

Speed must be positive so x = 5 is the required speed.

Speed of water = 5 km/hr

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- Back to worksheet
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Quote on Mathematics

“Mathematics, without this we can do nothing in our life. Each and everything around us is math.

Math is not only solving problems and finding solutions and it is also doing many things in our day to day life. They are:

It subtracts sadness and adds happiness in our life.

It divides sorrow and multiplies forgiveness and love.

Some people would not be able accept that the subject Math is easy to understand. That is because; they are unable to realize how the life is complicated. The problems in the subject Math are easier to solve than the problems in our real life. When we people are able to solve all the problems in the complicated life, why can we not solve the simple math problems?

Many people think that the subject math is always complicated and it exists to make things from simple to complicate. But the real existence of the subject math is to make things from complicate to simple.”