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A mathematician's way of converting miles to kilometers

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Re: A mathematician's way of converting miles to kilometers

#41

Post by OJFord »

phkahler wrote: post #34
mkagenius wrote: post #33

Earlier quoted context omitted.

Not if you just remember 3,5,8,13 . You do not need to remember all fibonacci numbers, just the above and rest you can multiple by 2,5,10 and get them

How many km is 4 miles? That's not on the list of numbers.

8 -> 13 and halve it for 6.5?

Or any other combination, but using a higher Fibonacci number is going to be more accurate than combining smaller ones.

Or in this case, as it's only 1 off a Fibonacci number you can convert that one and add 1.6 without multiplying it by anything (multiplying by the 1 off).

Re: A mathematician's way of converting miles to kilometers

#42

Post by CapricornNoble »

phkahler wrote: post #34
mkagenius wrote: post #33

Earlier quoted context omitted.

Not if you just remember 3,5,8,13 . You do not need to remember all fibonacci numbers, just the above and rest you can multiple by 2,5,10 and get them

How many km is 4 miles? That's not on the list of numbers.

I would solve it mentally as 4 miles = 3 miles + 1 mile.

3 miles ~=5km

1 mile = 1.6km

So 5km + 1.6km ~= 6.6km

Re: A mathematician's way of converting miles to kilometers

#44

Post by OJFord »

adtac wrote: post #39
phkahler wrote: post #34

Earlier quoted context omitted.

How many km is 4 miles? That's not on the list of numbers.

4 is the average of 3 and 5, so its km value is the average of 5 and 8 (assuming the Fibonacci series to be a geometric progression as described in the tweet). While I can do this for 4km, I can't for different values like 9km. I've done the multiply-by-1.6 thing often enough by now to be fast enough at it, so I'll likely be sticking to it. This is a cool trick nevertheless.

Or use them in combination:

9 is 8 + 1, so that's 8->13 + 1*1.6 = 14.6

Re: A mathematician's way of converting miles to kilometers

#46

Post by jedberg »

ghaff wrote: post #14
dEnigma wrote: post #10

Fascinating that the second reply (or second best reply?) is an unreasonably angry response: Who the hell needs all this .. Get lost [angry emoji]

There are a fair number of people who seem to take personal offense that the US (and to some degree the UK) don't use SI for everyday types of things and add it to their laundry list of grievances about the US generally. Never mind the fact that SI is generally used for engineering and other areas where it has legitimate advantages (which miles vs. kilometers doesn't really in day-to-day life).

> which miles vs. kilometers doesn't really in day-to-day life

Standard units are much more useful in carpentry. It's a lot easier when you can divide by 2,3,4, and 6.

Re: A mathematician's way of converting miles to kilometers

#47

Post by pbhjpbhj »

toolslive wrote: post #28
nesadi wrote: post #25

Earlier quoted context omitted.

> that SI is generally used for engineering Except when it isn't? Are you telling me SI is used in engineering everywhere in the US? I've heard too many stories (especially accidents) to believe that in any way.

don't they still use pounds per square inch ? Now, in Europe (excluding the UK) they also still use some weird units from the past. Calories for example, and horse (!!) power.

We still use PSI for tyre pressures in UK, probably some other things too.

They're given in N/m^2, but all the petrol station machines are in PSI, probably because the numbers just fall better.

Re: A mathematician's way of converting miles to kilometers

#48

Post by Elte »

learnstats2 wrote: post #15

It's both easier and more accurate to multiply by 1.6

Yeah times 1.6 isn't too hard right? Just add 50% and 10% in succession, very easy to do in your head.

The other way around is trickier. I tend to divide by 8 (or /2/2/2) and multiply by 5, which is harder but still consists only of steps that are clearly defined in my head.

Re: A mathematician's way of converting miles to kilometers

#49

Post by ghaff »

jedberg wrote: post #46
ghaff wrote: post #14

Earlier quoted context omitted.

There are a fair number of people who seem to take personal offense that the US (and to some degree the UK) don't use SI for everyday types of things and add it to their laundry list of grievances about the US generally. Never mind the fact that SI is generally used for engineering and other areas where it has legitimate advantages (which miles vs. kilometers doesn't really in day-to-day life).

> which miles vs. kilometers doesn't really in day-to-day life Standard units are much more useful in carpentry. It's a lot easier when you can divide by 2,3,4, and 6.

Yep. Factoring is useful in a lot of cases.

Also, although not strictly a debate around metric, the Fahrenheit scale gives you more granularity without going to decimals and requires less use of negative numbers on a day to day basis. And, if one is really concerned about a scientifically relevant temperature scale, we'd be using Kelvin, not Celsius.

Re: A mathematician's way of converting miles to kilometers

#50

Post by runarberg »

jedberg wrote: post #46
ghaff wrote: post #14

Earlier quoted context omitted.

There are a fair number of people who seem to take personal offense that the US (and to some degree the UK) don't use SI for everyday types of things and add it to their laundry list of grievances about the US generally. Never mind the fact that SI is generally used for engineering and other areas where it has legitimate advantages (which miles vs. kilometers doesn't really in day-to-day life).

> which miles vs. kilometers doesn't really in day-to-day life Standard units are much more useful in carpentry. It's a lot easier when you can divide by 2,3,4, and 6.

I've heard that and I don't disagree with it. But things fail really badly. E.g. 2 inches and 5 sixteenth
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