Simple Maths Problem

[dr_gn]

Einion Yrth said:

After consideration, it is clear that the "correct" answer is 7/48. It is also clear that the setter merely wished to test the students' ability to find the lowest common denominator and perform a subtraction between fractions.
Conclusion; the setter's an idiot.

Yup. Plus it’s a revision book for SATS, so the last thing a 9 year old needs is to be confused/frustrated when they’re already feeling a bit of pressure, and trying to learn.

[dr_gn]

anonymous said:

[redacted]

You didn’t define the question though:

It’s entirely correct if you ask the question “how much cake is left in terms of the percentage of a whole cake?”

It’s entirely incorrect if you simply ask “how much cake is left?”

[anonymous-user]

dr_gn said:

anonymous said:

[redacted]

You didn’t define the question though:

It’s entirely correct if you ask the question “how much cake is left in terms of the percentage of a whole cake?”

It’s entirely incorrect if you simply ask “how much cake is left?”

Obviously applying the question in the same context as the OP.
What fraction of the cakes?

[dr_gn]

anonymous said:

[redacted]

I am the OP!

Just saying that it depends entirely on wording. It never occurred to me that the answer to the original question could be anything other than 7/48.

[TwigtheWonderkid]

Northbloke said:

Many years ago we had the Monty Hall debate in our office and one chap, senior and very well educated, just would not accept the answer. We had to create a mockup of the problem using flipcharts and go through the motions to see what results came out. Unfortunately out of about 20 goes we only won something like 11 times by switching so closer to his wrong answer than the correct one! So he still wasn't convinced.

I find the best way of convincing someone of the Monty Hall problem is to ask the same question but with 1000 doors. A car behind one, and 999 goats.

You select your door number, 168. Monty opens all the doors, apart from your selection, 168, and number 709. He then asks you if you want to swap. People will say of course they want to swap, 709 is almost certainly where the car is. You then say "why? When I asked with 3 doors you said it made no odds to swap or not, it was 50/50. So why not 50/50 now. Only 2 options, and 1 car." Then the penny usually drops.

[V8LM]

Easiest way I've found to explain it is that after the first choice the probability that the car is behind one of the two doors not chosen in 2/3. The host then shows which one of these two it isn't behind, so the probability that it is behind the other one is 2/3.

[Some Gump]

I find it amazing that anyone can have a grasp of maths this bad, especially the f1 stats guru.

Only got though page 1, but throughout I was subconsciously adopting that sad downward headshake teachers use a lot!

[TwigtheWonderkid]

Some Gump said:

I find it amazing that anyone can have a grasp of maths this bad,

This is nothing. I got into a row on a thread about the lotto, with someone who said that if the chances of winning were 1 in 45m, if you bought 2 tickets, your chances weren't 1 in 22.5m, but 2 in 45m, which was an entirely different thing. And a few people waded in to support him!!

[Morningside]

TwigtheWonderkid said:

Some Gump said:

I find it amazing that anyone can have a grasp of maths this bad,

This is nothing. I got into a row on a thread about the lotto, with someone who said that if the chances of winning were 1 in 45m, if you bought 2 tickets, your chances weren't 1 in 22.5m, but 2 in 45m, which was an entirely different thing. And a few people waded in to support him!!

Don't worry I still get people who buy 6 scratch cards because it's 1 in 5 being a winner. They are still genuinely shocked when they don't win and shout fraud!

[dr_gn]

Some Gump said:

I find it amazing that anyone can have a grasp of maths this bad, especially the f1 stats guru.

Only got though page 1, but throughout I was subconsciously adopting that sad downward headshake teachers use a lot!

Out of interest, what answer do you think it is?

[TwigtheWonderkid]

Morningside said:

TwigtheWonderkid said:

Some Gump said:

I find it amazing that anyone can have a grasp of maths this bad,

This is nothing. I got into a row on a thread about the lotto, with someone who said that if the chances of winning were 1 in 45m, if you bought 2 tickets, your chances weren't 1 in 22.5m, but 2 in 45m, which was an entirely different thing. And a few people waded in to support him!!

Don't worry I still get people who buy 6 scratch cards because it's 1 in 5 being a winner. They are still genuinely shocked when they don't win and shout fraud!

Maybe we should run a competition for the most maths illiterate thing you've ever heard. I'll start with a woman in my office, when fuel prices hit £1.50 a litre a couple of years back and everyone was grumbling, she smugly announced "I'm lucky, it has no effect on me because I just put in £30 worth each time".

[AJB]

As pretty much now agreed 7/48, although 7/24 was the first answer that I reached.

But the real solution, which would have avoided 6 pages of arguments, would just have been to eat all of both of the cakes! Leaving food is always a mistake...

[FarmyardPants]

This thread just goes to show you can't have your cake and eat them.

[JuniorD]

dr_gn said:

Here's the question:

There are two identical cakes. Person A takes 5/6 of one cake, person B takes 7/8 of the other cake. What fraction of the cakes is left?

It's a terrible question, and without a definition or explanation of "takes" opens up a large number of possibilities. Takes where, and does what? Takes to a place nearby on a table, or takes and eats?

Quite conceivably all of the cake is left.