Author Topic: Arithmetic that makes you cringe  (Read 78011 times)

Re: Arithmetic that makes you cringe
« Reply #125 on: 02 October, 2019, 01:41:43 pm »
No, you'd be putting 10 times too much on!

1ml = 10-6m3
1ha = 104m2
1ml/ha = 10-6/104m = 10-10m = 1 ångström

Mind you, my experience of applying agri-death is that it's nigh-impossible to spray anything like evenly.

Cudzoziemiec

  • Ride adventurously and stop for a brew.
Re: Arithmetic that makes you cringe
« Reply #126 on: 02 October, 2019, 02:56:52 pm »
Financial analyst: What are the prospects for Product X?
Big boss: Product X sells £3.2 million, which is 8% of total sales. We have the capacity to increase that to 15%.
FA: Okay... my maths isn't that great.
BB: Alright, we can basically almost double it.
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T42

  • Apprentice geezer
Re: Arithmetic that makes you cringe
« Reply #127 on: 02 October, 2019, 03:26:26 pm »
Wikipedia tells me CGS = centimetre, gram, second and MKS = metre, kilogram, second. To my mind these are the same system, just at different scales. Isn't half the point of metric/SI that it's easy to relate between different scales because everything goes up and down in 10s, rather than an assortment of 12s, 16s, 20s and whatever in Imperial (and various other pre-metric systems)?

The danger with metric-based systems is losing track of the decimal point.  I did this during my A-level physics practical and the invigilator, who was wandering round making sure nobody was using a crafty AVOmeter, glanced at my pad and murmured "you might want to check that" as he passed my bench.
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fuaran

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Re: Arithmetic that makes you cringe
« Reply #128 on: 02 October, 2019, 03:49:58 pm »
Financial analyst: What are the prospects for Product X?
Big boss: Product X sells £3.2 million, which is 8% of total sales. We have the capacity to increase that to 15%.
FA: Okay... my maths isn't that great.
BB: Alright, we can basically almost double it.
Depends on whether the total sales stay the same, or increase, or decrease...

Re: Arithmetic that makes you cringe
« Reply #129 on: 02 October, 2019, 03:57:10 pm »
The danger with metric-based systems is losing track of the decimal point.  I did this during my A-level physics practical and the invigilator, who was wandering round making sure nobody was using a crafty AVOmeter, glanced at my pad and murmured "you might want to check that" as he passed my bench.
Indeed.  We (structural engineers) measure on site to mm, but work out loads in kN/m2 or kN/m.  Steel section serial sizes are related to the dimension in mm, but the tables of section properties quote Z in cm3 and I in cm4 (zenzizenzic centimetres, FYI).  Yield strengths of steels are quoted in MPa (N/mm2 or 103kN/m2).  Young's modulus is quoted in GPa (kN/mm2).

Cudzoziemiec

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Re: Arithmetic that makes you cringe
« Reply #130 on: 02 October, 2019, 04:20:59 pm »
Financial analyst: What are the prospects for Product X?
Big boss: Product X sells £3.2 million, which is 8% of total sales. We have the capacity to increase that to 15%.
FA: Okay... my maths isn't that great.
BB: Alright, we can basically almost double it.
Depends on whether the total sales stay the same, or increase, or decrease...
Not really. The question was about capacity not potential sales. The FA simply had to realize that 15 is approximately double 8.
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Cudzoziemiec

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Re: Arithmetic that makes you cringe
« Reply #131 on: 16 December, 2019, 11:49:49 am »
Quote
Across the Bristol area, roughly three in four people over the age of 18 voted in the General Election. Across the country, it was fewer than two in three.

Nationally, turnout in the 2019 election was 67.2 per cent - down 1.6 per cent on the poll in 2017.
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Giraffe

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Re: Arithmetic that makes you cringe
« Reply #132 on: 17 December, 2019, 08:56:58 am »
Quote
Across the Bristol area, roughly three in four people over the age of 18 voted in the General Election. Across the country, it was fewer than two in three.

Nationally, turnout in the 2019 election was 67.2 per cent - down 1.6 per cent on the poll in 2017.
So, fewer means either one or none.
Also, the bit "roughly three in four people over the age of 18 voted" seems to be either redundant or leaves me wondering about the proportion of under-18 voters.
2x4: thick plank; 4x4: 2 of 'em.

Re: Arithmetic that makes you cringe
« Reply #133 on: 18 December, 2019, 07:54:26 am »
Also, the bit "roughly three in four people over the age of 18 voted" seems to be either redundant or leaves me wondering about the proportion of under-18 voters.
Mr. Drumpf would say they were the Hillary voters.

Would it be clearer to say "roughly three in four people of voting age voted" ?

ElyDave

  • Royal and Ancient Polar Bear Society member 263583
Re: Arithmetic that makes you cringe
« Reply #134 on: 18 December, 2019, 09:07:30 am »
surely the easiest way would be to say 2sq.m and 2m2 to avoid confusion?  Happens regularly in my industry - both the designations and confusion
“Procrastination is the thief of time, collar him.” –Charles Dickens

ian

Re: Arithmetic that makes you cringe
« Reply #135 on: 18 December, 2019, 09:17:39 am »
Also, the bit "roughly three in four people over the age of 18 voted" seems to be either redundant or leaves me wondering about the proportion of under-18 voters.
Mr. Drumpf would say they were the Hillary voters.

Would it be clearer to say "roughly three in four people of voting age voted" ?

Why not just three quarters in Bristol compared with two-thirds across the country. When did fractions become so vulgar?

Cudzoziemiec

  • Ride adventurously and stop for a brew.
Re: Arithmetic that makes you cringe
« Reply #136 on: 18 December, 2019, 09:27:54 am »
Quote
Across the Bristol area, roughly three in four people over the age of 18 voted in the General Election. Across the country, it was fewer than two in three.

Nationally, turnout in the 2019 election was 67.2 per cent - down 1.6 per cent on the poll in 2017.
So, fewer means either one or none.
Also, the bit "roughly three in four people over the age of 18 voted" seems to be either redundant or leaves me wondering about the proportion of under-18 voters.
Good point about fewer, but if that were the problem, it would be in the Grammar thread. All I noticed is that 67.2% is more than two in three.
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Re: Arithmetic that makes you cringe
« Reply #137 on: 16 January, 2020, 11:26:50 pm »
Quote
Kashmir covers around 86,000 sq miles (138 sq km), and is famed for the beauty of its lakes, meadows and snow-capped mountains.

From https://www.bbc.co.uk/news/world-asia-51131294
Rust never sleeps

Ben T

Re: Arithmetic that makes you cringe
« Reply #138 on: 16 January, 2020, 11:45:44 pm »
If you order something that's basically a closed flexible band, that's to go round something round, and it's described as having "diameter: 4cm".
When you get it, you lay it flat on a surface (so it's doubled up) and measure it. 4cm.
IS that it's diameter?? Cos to me, that's half the circumference.

Cudzoziemiec

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Re: Arithmetic that makes you cringe
« Reply #139 on: 27 January, 2020, 09:39:45 am »
Monday puzzle in that there Grauniad:
Quote
Here’s another numerical palindrome:

50, 20, 10, 01, 02, 05

It’s the pence value of the UK coins in circulation under a pound.

What is the highest value of UK coins you can have in your pocket without being able to exchange them exactly for a £10 note?

(This puzzle is filed under. ‘Not difficult but you’d be surprised at how many people get it wrong.’)
I don't get this. How could the answer possibly not be £9.99? But there must be something else cos that's just too obvious. Does he mean only using each value of coin once? Or what? It feels like there's some assumption that's so obvious he hasn't stated it but I'm missing it.
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nicknack

  • Hornblower
Re: Arithmetic that makes you cringe
« Reply #140 on: 27 January, 2020, 10:17:11 am »
Monday puzzle in that there Grauniad:
Quote
Here’s another numerical palindrome:

50, 20, 10, 01, 02, 05

It’s the pence value of the UK coins in circulation under a pound.

What is the highest value of UK coins you can have in your pocket without being able to exchange them exactly for a £10 note?

(This puzzle is filed under. ‘Not difficult but you’d be surprised at how many people get it wrong.’)
I don't get this. How could the answer possibly not be £9.99? But there must be something else cos that's just too obvious. Does he mean only using each value of coin once? Or what? It feels like there's some assumption that's so obvious he hasn't stated it but I'm missing it.
Dunno what the actual answer is, but if you had a 19x50s and 3x20s then you'd have £10.10 which is more than £9.99.
<thinks>
Or 49x20s and 1x50 = £10.30
There's no vibrations, but wait.

Re: Arithmetic that makes you cringe
« Reply #141 on: 27 January, 2020, 10:19:02 am »
My interpretation is

Quote
What is the highest value of UK coins you can have in your pocket without being able to exchange some of them exactly for a £10 note?

If you had 49no 20pences and 1no 50pence, you'd have £10.30, but wouldn't be able to make £10.  I think this is the solution.

See also: 43 Chicken McNuggets

Edit: cross-posted with nicknack!

Phil W

Re: Arithmetic that makes you cringe
« Reply #142 on: 27 January, 2020, 10:47:14 am »
You could also add 5p and 2 x 2p to that and still not be able to make up £10, so £10.39

Re: Arithmetic that makes you cringe
« Reply #143 on: 27 January, 2020, 11:17:24 am »
Good spot!

Cudzoziemiec

  • Ride adventurously and stop for a brew.
Re: Arithmetic that makes you cringe
« Reply #144 on: 27 January, 2020, 11:23:16 am »
My interpretation is

Quote
What is the highest value of UK coins you can have in your pocket without being able to exchange some of them exactly for a £10 note?

If you had 49no 20pences and 1no 50pence, you'd have £10.30, but wouldn't be able to make £10.  I think this is the solution.
Okay, that makes sense. And Nicknack's answer, which has the advantage of being almost palindromic.

Quote
See also: 43 Chicken McNuggets
What?  ???
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Re: Arithmetic that makes you cringe
« Reply #145 on: 27 January, 2020, 12:40:39 pm »
43 is the largest number of Chicken McNuggets which couldn't be made using the standard sized packs (6, 9, 20).

Cudzoziemiec

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Re: Arithmetic that makes you cringe
« Reply #146 on: 27 January, 2020, 02:15:21 pm »
43 is the largest number of Chicken McNuggets which couldn't be made using the standard sized packs (6, 9, 20).
This is why McDonalds have their own university!
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Wowbagger

  • Former Sylph
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Re: Arithmetic that makes you cringe
« Reply #147 on: 27 January, 2020, 02:22:22 pm »
43 is the largest number of Chicken McNuggets which couldn't be made using the standard sized packs (6, 9, 20).

This reminds me of a rather neat problem I recall from my primary school teaching days.

A 40kg weight drops on the floor and breaks into 4 pieces. It so happens that the pieces are precisely the correct mass to allow any number of whole kilograms from 1 to 40 to be weighed on a balance. What is the mass of each of the 4 pieces?
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rr

Re: Arithmetic that makes you cringe
« Reply #148 on: 27 January, 2020, 04:15:40 pm »
You could also add 5p and 2 x 2p to that and still not be able to make up £10, so £10.39
Can't you have 4×2p, making £10.43?

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rr

Re: Arithmetic that makes you cringe
« Reply #149 on: 27 January, 2020, 05:27:08 pm »
You could also add 5p and 2 x 2p to that and still not be able to make up £10, so £10.39
Can't you have 4×2p, making £10.43?

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Indeed you can, the answer is £10.43

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