# miles per hour?

-- Last Updated: Aug-05-08 12:21 PM EST --

I paddled 4 miles exactly in 38 minutes. Trying to figure out what my speed was (no gps with me) and this is the only way I know how to do it.

(It was a great run with a 10 mile an hour beam wind) Night heron and my own carved GP. )

Distance = Rate x Time

So in the case of today, I paddled 4 miles in 38 minutes

4 miles = Rate x 38/60 (60 minutes) or…19/30 (which is the same fraction)

__4___

19 over 30

Which would be the exact same thing as:

4 x 30 = 120

divided by 19

120 divided by 19 = 6.315 miles per hour (Not too bad for an old fart)

Whew!

Do anyone have an easier way to do this?????

Sure do…
Lie!

Sure

– Last Updated: Aug-05-08 12:30 PM EST –

1 hour = 60 minutes

38 minutes/60 minutes = 0.6333 hours

4 miles/.6333 hours = 6.316 miles/hour

I think this is easier
4/38 = x/60, 38 and 60 being minutes

You multiply the cross-numbers to immediately get

240 = 38x

x = 240/38 = 6.3 etc.

For nautical miles (if I have the multiplier right), it’d start out

(4 times 1.12)/38 = x/60

Rest works the same way.

Geez
Before I bought a bike computer, I used to manually calculate my miles per hour. Using miles ridden in time elapsed was most accurate, but sometimes I would estimate it by using crank rpms and gear ratios. THAT was more of a pain to do.

Is this a trick question?Calculator.

4 miles?
You want an exact mph but without a gps you hve no idea of your exact milage. If it is that important to know how fast you are going - buy a GPS. I find it a great tool to have on the water. I have an inexpensive hand held one and find it very useful on the water for reading currents and for navigation.

Taylor Series
4/ ( 38/60) = 460/38=240/38=240/( 40(1 - 1/20))=

240/40*(1+1/20)=6*(1+1/20)=6+6/20=6.3

Basically, goes like this:

Closest easy number is 40, 38 is -2/40=-1/20 away, the fractional correction will be +1/20

So, 40 minutes = 6mph, +1/20*6 = 6.3

Example - you did 4m in 41min. Correction -1/40. So, 6mph, -1/40 * 6 = 5.85mph

Since this is 1st order approximation, smaller fractions will yield more exact results

It’s a boat - use knots
1 nautical mile is pretty close to 6000 feet.

That lets 1 knot (a knot is 1 nautical mile per hour) equal about 100 feet per minute.

4 statue miles = 21120 feet (1 statute mile is 5280 feet)

21120 feet / 38 minutes = 555 feet per minute

555/100 = 5.5 knots

???
I had both shoes off by the third sentence. I usually ask the person I’m paddling with.

Sure do…
Post the info on this board and let the p.netters do the math.

Simple!

G_K

Knots are useless on inland waters
The fact that you travel by boat is irrelevant with respect to what units you “should” use to report your speed. If the only maps available of your waterways are scaled in miles (and that’s true for most of us), then determining your speed in knots only guarantees that you will THEN have to do some math to translate that to units that makes sense when applied to the map.

4 x 60 / 38 = 6.316

Oh, but “knots” sounds more nautical
My husband came back from a guided day trip on Lake Erie and used “knots per hour”. I wanted to gag. The usage had nothing to do with maps. It was purely for show.

raaaaaaaaaalph

I do have a gps.

– Last Updated: Aug-05-08 2:00 PM EST –

works great. Even better when I remember to bring it.

I paddle this run almost every morning lately. it is the Lake Murray dam which is exactly two miles across if you paddle to the 2nd buoy at the end of the beach side of the dam and back. I know this because I purposely charted it to be 4 miles with the GPS!

the real answer is who cares? Did I have fun?

YES!

That’s the main thing
Which boat were you in? My guess is the Outer Island…

I usually remember to bring my GPS
But a new set of batteries after the ones in the unit go dead after 5 minutes is another story.

the boat and the run

– Last Updated: Aug-05-08 2:10 PM EST –

Boat was the wood strip Night heron with a GP. OI might be a little faster.

nick
designs a lovely boat.

see the math in above posts.

Furlongs per fortnight

– Last Updated: Aug-05-08 2:50 PM EST –

are so much easier to use but my GPS just will not display in those units :)

Mark - former chemical engineering student