Question

Please help my brain is fried. :(
David rowed a boat upstream for three miles and then returned to point he started from. The entire journey took four hours. The speed of the stream is one mile per hour. Find David's speed in still water. David's speed in still water is ? miles per hour?

Answer 1

speed = distance ÷ time, upstream speed = speed of the boat – speed of the stream, and downstream speed = speed of the boat + speed of the stream

Answer 2

@iGreen u busy?

Answer 3

@Directrix any ideas

Answer 4

s=6 divided by 4 =3/2=1.5 s=1.5

Answer 5

upstream speed =1.5-1=0.5 so upstream speed is 0.5

Answer 6

downstream = 1.5+1=2.5

Answer 7

Need to find the speed in still water?

Answer 8

@jim_thompson5910 are u busy?

Answer 9

Upstream: 3 = (r - 1) * (t) where r is the boat speed in still water and t is the time spent rowing upstream.

Downstream: 3 = (r + 1) * (4 - t)

So, 3 = (r - 1) * (t) = (r + 1) * (4 - t)

See what you think. It's just an idea.

Answer 10

So,
(r - 1) * (t) = (r + 1) * (4 - t)

Answer 11

Which gives a rate of 2. I wish we could get somebody over here to check. I think that the notification features are malfunctioning on OS tonight.

Answer 12

yeah OS isnt working to well

Answer 13

Do you think 2 is incorrect? @KitKat16

Answer 14

Still water speed of boat checks out at 2 miles per hour.

Answer 15

Thanks, @kropot72

Answer 16

Thanks guys for the help! :)

Answer 17

You're welcome :)