Author Topic: Education and Schools  (Read 234 times)

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Ian

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Education and Schools
« on: January 23, 2021, 12:31:44 PM »
A place to debate knotty problems
“Nothing is so firmly believed as that which we least know.”   ― Michel de Montaigne

Si hoc legere scis, nimis eruditionis habes.

Ian

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Re: Education and Schools
« Reply #1 on: January 23, 2021, 12:35:42 PM »
From the DP:

"Work set by teachers has left many digging out their calculators and trying to remember how to do algebra and equations.

But even work being set by primary schools is proving to be tricky, with families turning to social media and forums for help.

One mum had her friends and family scratching their heads trying to work out a maths problem that was set for her eight-year-old son.

She said: "I was trying to work it out all day and wondered whether it was me just being thick. I thought it was really hard for an eight-year-old."

The problem  was this:

The aquarium has 198 guppies, angelfish and catfish altogether.
There are 4 times as many guppies as angelfish.
There are 6 more angelfish than catfish.

How many catfish are there?


Part of the problem (quite a huge part) is the way in which the question is asked. In the real world, we'd simply count the catfish. But some teachers and some who set maths problems thrive on making the question far harder than it needs to be.

Try to solve it before reading the solution, posted below.
“Nothing is so firmly believed as that which we least know.”   ― Michel de Montaigne

Si hoc legere scis, nimis eruditionis habes.

Ian

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Re: Education and Schools
« Reply #2 on: January 23, 2021, 12:37:07 PM »
The solution:

It's solutions like this that convinced me that maths was essentially illogical. But see what you think.

I’m going to refer to the guppies as “g”, the angelfish as “a” and the catfish as “c”.

We know there are 198 altogether.

g + a + c = 198

There are 4 times as many guppies as angelfish, so 4 lots of angelfish is the same as the number of guppies

4a = g

And also, we know that there are 6 more angelfish than catfish, so catfish is angelfish minus 6

a – 6 = c

If we substitute the g and c into the first equation, we get

4a + a + a – 6 = 198

Tidying this up gives us 6a = 204 (we’ve added 6 to both sides of the equation )

So a = 34  (angelfish)

We know that catfish is angelfish minus 6, so catfish = 28

We also there are 4 times as many guppies as angelfish, so guppies = 136

Just to check we need g + a + c = 198

34 + 28 + 136 does equal 198.

So the answer is 28.
“Nothing is so firmly believed as that which we least know.”   ― Michel de Montaigne

Si hoc legere scis, nimis eruditionis habes.

DVT

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Re: Education and Schools
« Reply #3 on: January 23, 2021, 03:45:23 PM »
The question is flawed!

By the time you've worked it out the guppies will have reproduced and increased their number !!!

Ian

  • Administrator
Re: Education and Schools
« Reply #4 on: January 23, 2021, 06:27:51 PM »
Exactly! The question is not only unrealistic and as far removed from real world problems as it's possible to be, but it's asked in the most confusing way imaginable.
“Nothing is so firmly believed as that which we least know.”   ― Michel de Montaigne

Si hoc legere scis, nimis eruditionis habes.