going down the river a boat went 18km/h. Going up the river it only went 4km/h. Find the speed of the boat in still water and th

Question

3 years ago

13

e speed of the current.

1 answer:

jarptica [38.1K] · Answer 1 · 2022-07-15T04:56:09+03:00

The speed of boat is 11 km/h in still water and speed of current is 7 km/h.

Step-by-step explanation:

Combined speed of boat and current while going down = 18 km/h

Combined speed while coming up = 4 km/h

Let,

Speed of boat = x

Speed of current = y

As boat and current were in same direction while going down,

x+y = 18 Eqn 1

We will subtract the speed of current while coming up because both the boat and current will be in opposite directions.

x-y = 4 Eqn 2

Adding Eqn 1 and Eqn 2

$(x+y)+(x-y)=18+4\\x+y+x-y=22\\2x=22$

Dividing both sides by 2

$\frac{2x}{2}=\frac{22}{2}\\x=11$

Putting x=11 in Eqn 1

$11+y=18\\y=18-11\\y=7$

The speed of boat is 11 km/h in still water and speed of current is 7 km/h.

Keywords: linear equation, speed

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