Please check my Calculations

Not when you use the correct figure to four significant digits of 12.95.

Actually, both

(580 / 1.6093) / (49 / 3.785) = 27.8, to the nearest tenth, rounding the final
result correctly.

and

360.4 / 12.95 = 27.8, to the nearest tenth, rounding the final result correctly

If you want to get into the rules of significant digits rounding, feel free. But
I suspect

 

Not when you use the correct figure to four significant digits of 12.95.

Actually, both

(580 / 1.6093) / (49 / 3.785) = 27.8, to the nearest tenth, rounding the final
result correctly.

and

360.4 / 12.95 = 27.8, to the nearest tenth, rounding the final result correctly

If you want to get into the rules of significant digits rounding, feel free. But
I suspect

 

I would like to get into those rules. What do you think of my practice of
rounding numbers that end in 5: even numbers like 85 go down to 8; odd like
75 go up to 8. That way, on average, no bias is introduced.

 

I would like to get into those rules. What do you think of my practice of
rounding numbers that end in 5: even numbers like 85 go down to 8; odd like
75 go up to 8. That way, on average, no bias is introduced.

 

This is a test, right?

85 is not an even number. ;-)

Otherwise, whether your rule is useful depends on your mathematical goal.

 

This is a test, right?

85 is not an even number. ;-)

Otherwise, whether your rule is useful depends on your mathematical goal.

 

There's an easier way by using the Google calculator. For those that
do not know about it, here's how:

1. You need to know how many km/l your car can drive, which is very easy:

580km / 49l = 11.86km/l

2. Go to www.google.com and type in the search box:

11.86km/l = ? miles/gallon

The answer google returned was 27.89 miles/gallon which is very close to
your result. The default in google is in US gallons, but you can specify
Imperial (British) gallons as well.

Give the Google calculator a try, it really comes in handy, and not just
for converting from metric to imperial (and vice-versa).

Cosmin

 

There's an easier way by using the Google calculator. For those that
do not know about it, here's how:

1. You need to know how many km/l your car can drive, which is very easy:

580km / 49l = 11.86km/l

2. Go to www.google.com and type in the search box:

11.86km/l = ? miles/gallon

The answer google returned was 27.89 miles/gallon which is very close to
your result. The default in google is in US gallons, but you can specify
Imperial (British) gallons as well.

Give the Google calculator a try, it really comes in handy, and not just
for converting from metric to imperial (and vice-versa).

Cosmin

 

Thank you all who replied...

Arthur, if you get some data on when to change gears, please post that to group.

 

the reason why the cut off is '5'....

0,1,2,3,4 round down (preceding digit is not advanced)
5,6,7,8,9 round up (preceding digit is advanced)


which gives us an even split

 

the reason why the cut off is '5'....

0,1,2,3,4 round down (preceding digit is not advanced)
5,6,7,8,9 round up (preceding digit is advanced)


which gives us an even split

 

Well, we could argue about what is least significant, but it would be a
useless exercise. As far as gas mileage is concerned, I would think a
single decimal place would be proper, as the error is small.

The 12.94, that would be rounded to 12.9, keeping it constant if it is
decided to use 3 significant digits, which would yield a 27.9 final tally.
Either way, both numbers are <.2% off from the 27.85 figure. This margin of
error could be deemed acceptable. Without having an actual tolerance, it is
impossible to tell what really is least significant.

 

Well, we could argue about what is least significant, but it would be a
useless exercise. As far as gas mileage is concerned, I would think a
single decimal place would be proper, as the error is small.

The 12.94, that would be rounded to 12.9, keeping it constant if it is
decided to use 3 significant digits, which would yield a 27.9 final tally.
Either way, both numbers are <.2% off from the 27.85 figure. This margin of
error could be deemed acceptable. Without having an actual tolerance, it is
impossible to tell what really is least significant.

 

No need to round a "0". It's already there.

 

No need to round a "0". It's already there.

 

Ah, good one, thanks. I'd used google's calculator a time or two for
simple expressions but didn't know it could accept equations. You've
prompted me to read a bit more about it, and it seems quite flexible.
From your example above,

11.86km/l=?mi/gal

and

11.86km/l in mi/gal

give the same result, and for example

32c=?f

or

32c in f

converts 32 degrees Centigrade into degrees Farenheit. But how do we
know which units are convertible? From

http://www.google.com/help/calculator.html

"The calculator understands many different units, as well as many
physical and mathematical constants. These can be used in your
expression. Many of these constants and units have both long and short
names. You can use either name in most cases. For example, km and
kilometer both work, as do c and the speed of light.

Feel free to experiment with the calculator as not all of its
capabilities are listed here."

Ha! Ah well, perhaps they'll add a units key soon. I'd been using

http://www.onlineconversion.com

but access to Google is quicker.

-------
NB: If response to this post does not concern the calculator, please
delete k12.ed.math and sci.math newsgroups from your post, thanks.

(Mutter, mutter, now lessee, 2 mi = ? nautical miles...ah, works.
Hmm, what about deg-min-sec to UTM...)

 

Ah, good one, thanks. I'd used google's calculator a time or two for
simple expressions but didn't know it could accept equations. You've
prompted me to read a bit more about it, and it seems quite flexible.
From your example above,

11.86km/l=?mi/gal

and

11.86km/l in mi/gal

give the same result, and for example

32c=?f

or

32c in f

converts 32 degrees Centigrade into degrees Farenheit. But how do we
know which units are convertible? From

http://www.google.com/help/calculator.html

"The calculator understands many different units, as well as many
physical and mathematical constants. These can be used in your
expression. Many of these constants and units have both long and short
names. You can use either name in most cases. For example, km and
kilometer both work, as do c and the speed of light.

Feel free to experiment with the calculator as not all of its
capabilities are listed here."

Ha! Ah well, perhaps they'll add a units key soon. I'd been using

http://www.onlineconversion.com

but access to Google is quicker.

-------
NB: If response to this post does not concern the calculator, please
delete k12.ed.math and sci.math newsgroups from your post, thanks.

(Mutter, mutter, now lessee, 2 mi = ? nautical miles...ah, works.
Hmm, what about deg-min-sec to UTM...)

 

1000 meters will cut your horsepower output by 11%. I lived at 3000
feet for 5 years and that was the concensus in the automotive world
there. Atmospheric O2 pressure is essentially a logarithmic function
of the altitude, so it is not proportional and you can't "eyeball" the
power loss at other altitudes using this figure.

The altitude will not directly affect your mileage, at least on modern
FI cars. But, since you have to rev the engine harder to keep up
decent torque, there will be small additional friction losses due to
the higher rpm. Also its harder on your ears to drive this way, so
maybe some people will settle for lower engine output in the first
place.

JM

 

1000 meters will cut your horsepower output by 11%. I lived at 3000
feet for 5 years and that was the concensus in the automotive world
there. Atmospheric O2 pressure is essentially a logarithmic function
of the altitude, so it is not proportional and you can't "eyeball" the
power loss at other altitudes using this figure.

The altitude will not directly affect your mileage, at least on modern
FI cars. But, since you have to rev the engine harder to keep up
decent torque, there will be small additional friction losses due to
the higher rpm. Also its harder on your ears to drive this way, so
maybe some people will settle for lower engine output in the first
place.

JM

 

IIRC Honda didn't get that, the EPA did. Overall my '03 Accord EX sedan
w/automatic has gotten 26 mpg (12,500 miles). I consistently get > 30
mph on the highway, with a max going to NC of 34 mpg (absolutely NO city
driving & no A/C).