Question

David is rowing a boat upstream. The river is flowing at a speed of 2 miles per hour. David starts rowing at a speed of 6 miles per hour, but as he gets tired his speed decreases (at a rate of 1 mile per hour, every hour). Which equation represents the speed of the boat for x hours spent rowing?

Answer 1

Y=4-x
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Answer 2

Answer: The required equation is,

y = 4 - x

Step-by-step explanation:

Let x be the number of hours spent after David got tired and y represents his speed after x hours,

Given,

His initial speed in still water = 6 miles per hour,

Also, the speed of stream = 2 miles per hour,

So, his initial speed in upstream = 6 - 2 = 4 miles per hour,

Now, His speed is decreasing by 1 miles per hour in every hour,

Thus, total decrement in his speed after x hours = 1x = x

Hence, his speed after x hours = Initial speed in upstream - Decrement in speed

y = 4 - x

Which is the required equation.