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March 29, 2024, 03:20:57 am

Author Topic: Extension 1 - Particle Concentration Question  (Read 2999 times)  Share 

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Jefferson

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Extension 1 - Particle Concentration Question
« on: January 27, 2020, 02:15:38 pm »
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Hey Everyone,

I don't quite understand the wording of this question nor where to start (see attachment).
Any help is appreciated.

Thank you!

RuiAce

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Re: Extension 1 - Particle Concentration Question
« Reply #1 on: January 29, 2020, 11:53:58 pm »
+2
I can't be sure of this but at first glance it looks like it's just ratios.

Let \(x\) be the amount of concentration of tea we require. That is, a particle concentration of \(x\) should reduce to a particle concentration of 51.8g after passing through sieve B.

A particle concentration of 100g gets reduced to a concentration of 39.6g after passing through sieve B.
\[\text{So we just end up with}\\ \frac{100}{39.6} = \frac{x}{51.8}. \]
The only issue is that I can't justify why ratios work here. But the first thing I thought of was basically linear relationships.

Jefferson

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Re: Extension 1 - Particle Concentration Question
« Reply #2 on: January 30, 2020, 10:28:15 pm »
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I can't be sure of this but at first glance it looks like it's just ratios.

Let \(x\) be the amount of concentration of tea we require. That is, a particle concentration of \(x\) should reduce to a particle concentration of 51.8g after passing through sieve B.

A particle concentration of 100g gets reduced to a concentration of 39.6g after passing through sieve B.
\[\text{So we just end up with}\\ \frac{100}{39.6} = \frac{x}{51.8}. \]
The only issue is that I can't justify why ratios work here. But the first thing I thought of was basically linear relationships.

Thank you RuiAce! The answer is indeed 30.8 g (extra).
Is there any particular reason why they used the word "average" in the question, but not in the information given? :(
Also, I rarely see questions with this many excess information in mathematics. Is this something introduced in the new syllabus?

Thanks,
Jefferson

« Last Edit: January 30, 2020, 10:30:06 pm by Jefferson »

RuiAce

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Re: Extension 1 - Particle Concentration Question
« Reply #3 on: January 31, 2020, 03:17:49 am »
+1
Thank you RuiAce! The answer is indeed 30.8 g (extra).
Is there any particular reason why they used the word "average" in the question, but not in the information given? :(
Also, I rarely see questions with this many excess information in mathematics. Is this something introduced in the new syllabus?

Thanks,
Jefferson


I didn't notice that first time round actually. I feel like the word "average" should've shown up in the question as well. :(

For an assignment, I suppose it's fair enough. Assignments can be investigative tasks requiring students to determine for themselves what's useful. But if this question came from an exam, I would be raising eyebrows in confusion here.