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?
A.y=4-x
B.y=x-4
C.y=6-2x
D.y=6-x
E.y=x+4

Answer 1

Let's look at two things.
1. The speed of the boat upstream
2. How the speed looses speed each hour

Answer 2

okay

Answer 3

@mathstudent55

Answer 4

@maddiegirl

Answer 5

@shifuyanli

Answer 6

have u tried google?

Answer 7

Let's look at the first part.
He is rowing at a speed of 6 mph, and he is going upstream.
I'll assume that his speed of 6 mph is in still water. If he were rowing in a lake, for example, where there is no water current, his speed would be 6 mph. He is rowing in a river, and the river flows at 2 mph. Since he is rowing in a direction opposite the direction of the flow of the river, he loses the 2 mph of the river speed, so his speed is only 4 mph to start with.

Answer 8

Now let's look at the second part.
For each hour that he rows, he gets more and more tired and loses 1 mph of speed per hour.
In the first hour, his speed goes down by 1 * 1 mph
In the second hour, his speed goes down 1 * 2 mph
In the third hour, his speed goes down 1 * 3 mph
In hour x, his speed goes down 1 * x mph.
Since 1 * x is simply equal to x, his speed is going down by x.
A loss of speed means the speed he loses is subtracted from his original speed.

Answer 9

That means his speed, y, is 4 - x, so you have the equation:
y = 4 - x