8 Year Old's Maths Question

[srw]

Before you can answer a difficult question like that, first you'd have to establish that 1+1=2
https://blog.plover.com/math/PM.html

I once picked up a copy of Russell & Whitehead. I quickly realised I had neither the patience nor the attention to detail to do more than marvel at it. And since Gödel had wrecked their ultimate goal that it was a pretty futile idea anyway.

I did also once look at a copy of Euclid. Which once upon a time our notional 8-year-old would have been started on.

 

[MartinQ]

I did also once look at a copy of Euclid. Which once upon a time our notional 8-year-old would have been started on.

Elements?
https://www.gutenberg.org/files/21076/21076-pdf.pdf

There is quite a good book by Tony Gardiner for "advanced" gcse level which is more traditional subjects and much more about self discovery than rote learning
https://www.openbookpublishers.com/product/979

I'm going to get told off again, and its your fault

 

[Electric_Andy]

Ok assume that 0.9999... is less than 1. If you add something (> 0) to any of the digits, the result is > 1, so it must be the closest number to 1, but different.

Then
1 - 0.99999..... = a > 0 (say)
And
0.9999... < 0.9999... + a/2 < 1
But that can't be as 0.9999... is the closest number to 1. So 0.999... is not less than 1.

Any decimal which can be written down (finite) has this property so
3.6 = 3.59999999.....
Etc

ok, I sort of get it. I think context must come into play, which aslo narrows down recurring numbers. For example, if we're talking about dividing a pizza into 3, 0.33 would probably do. There would be no detectable nutritional deficit, nor visual difference (with the naked eye) if one portion was 0.339 and the other was 0.331. In terms of engineering (I am not an engineer) there's probably an enginieering standard which i would guess would not go beyond 0.001 of a mm. Do any engineers want to add?

 

[DaveReading]

ok, I sort of get it. I think context must come into play, which aslo narrows down recurring numbers. For example, if we're talking about dividing a pizza into 3, 0.33 would probably do. There would be no detectable nutritional deficit, nor visual difference (with the naked eye) if one portion was 0.339 and the other was 0.331. In terms of engineering (I am not an engineer) there's probably an enginieering standard which i would guess would not go beyond 0.001 of a mm. Do any engineers want to add?

An engineer wouldn't accept 0.33 as an approximation for 0.339

 

[Deleted member 26715]

An engineer wouldn't accept 0.33 as an approximation for 0.339

Depends what the drawing said.

 

[Ming the Merciless]

An engineer wouldn't accept 0.33 as an approximation for 0.339

Well they would, as engineering is about compromise. How precise does something need to be for it to work would be their question. If .33 or .34 makes not difference the. .339 would be fine

 

[Profpointy]

An engineer wouldn't accept 0.33 as an approximation for 0.339

Depends what's being engineered - width of a road in mm - fine. Dimensions of a turbine blade in metres, not so fine

 

[Beebo]

One hundredth of a mm is a very small tolerance.

 

[Deleted member 26715]

One hundredth of a mm is a very small tolerance.

I used to work to less I think, grinding Reamers for Dormer Tools

 

[Archie_tect]

If we're dividing a pizza into 3, can I have the biggest third...

 

[matticus]

If we're dividing a pizza into 3, can I have the biggest third...

That's a recurring demand.

 

[Archie_tect]

You can have the bit with the green peppers.

 

[Electric_Andy]

I must admit, doing some multiplication with my 7 year-old, I learned about doing the table method. I was never taught that in school. Who knows, if I had I might have had a completely different life!

 

[Deleted member 26715]

I must admit, doing some multiplication with my 7 year-old, I learned about doing the table method. I was never taught that in school. Who knows, if I had I might have had a completely different life!

"Table method" ?

 

[Electric_Andy]

"Table method" ?