a motorboat traveling with a current can go 160km in 4 hours. against the current it takes 5 hours to go the same distance. find the speed of motorboat and speed of current

Respuesta :

The speed of motorboat is 36 kmph and speed of current is 4 kmph.

Step-by-step explanation:

Distance covered in 4 hours = 160 km

Time took on return trip = 5 hours

Let,

x represent the speed of boat.

y represent the speed of current.

Combined speed of boat and current when in same direction = x+y

Speed of boat and current when travelling against = x-y

Distance = Speed * Time

Speed = [tex]\frac{Distance}{Time}[/tex]

x+y = [tex]\frac{160}{4}[/tex]

x+y = 40     Eqn 1

x-y =  [tex]\frac{160}{5}[/tex]

x-y = 32      Eqn 2

Adding Eqn 1 and Eqn 2

[tex](x+y)+(x-y)=40+32\\x+y+x-y=72\\2x=72[/tex]

Dividing both sides by 2

[tex]\frac{2x}{2}=\frac{72}{2}\\x=36[/tex]

Putting x=36 in Eqn 1

[tex]36+y=40\\y=40-36\\y=4[/tex]

The speed of motorboat is 36 kmph and speed of current is 4 kmph.

Keywords: linear equation, addition

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The Speed of motor boat is [tex]36\;\rm{km/hr}[/tex] and speed of current is [tex]4\;\rm{km/hr}[/tex].

Given information:

A motorboat traveling with a current can go [tex]160\;\rm{km[/tex] in [tex]4[/tex] hours. Against the current, it takes [tex]5[/tex] hours to go the same distance.

Let the speed of boat be u and speed of current be v.

Combined speed of boat and current when in same direction, u+v

And Speed of boat and current when travelling against, u-v

Now, Using the relation of Distance, speed and time, [tex]\rm{distance}={speed}\times{time}[/tex]

In case1: The motorboat traveling with a current, then formulated this situation in equation form we get:

[tex]u+v=\frac{160}{4} \\u+v=40\;\;\;..........(1)[/tex]

In case 2: The motorboat traveling against the current, then formulated this situation in equation form we get:

[tex]u-v=\frac{160}{5}\\u-v=32\;\;\;\'............(2)[/tex]

Adding equation [tex](1)[/tex] and [tex](2)[/tex] we get:

[tex]u+v+u-v=40+32\\[/tex]

                 [tex]2u=72\\[/tex]

                   [tex]u=36[/tex]

Substituting the value of [tex]u=36[/tex] in equation [tex](1)[/tex] we get,

[tex]36+v=40[/tex]

       [tex]v=4[/tex]

Therefore, Speed of motor boat is [tex]36\;\rm{km/hr}[/tex] and speed of current is [tex]4\;\rm{km/hr}[/tex].

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