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Can you solve the maths question for Singapore schoolkids that went viral?


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I got n=10 but by looking at the equation and seeing that it had to be 10 because (10x10) - 10=90.

 

Is all the stuff about sweets and probability a red herring? Do they teach probability at GCSE level now?

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Sorry chinahand. Had visitors, will ring you back shortly.

Looks to me like chinahands kitchen after he finished tiling it

Can you solve the maths question for Singapore schoolkids that went viral?

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All i got was there are 10 sweets in the bag.

 

edited to add pretty much same as you Declan,

 

either: 6/10 x 5/9 = 1/3 or 0.3333333

 

or 10 x 10 -10 -90 = 0

Edited by Lao
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Solving the equation to get n=10 wasn't the question - generating the equation was what was required. Tarne's solution is spot on.

 

In response to Declan - yes they do teach probability at GCSE. A modern feature however is to dress questions up in 'real life situations' - I don't know why.

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The great thing about maths is that the questions often contain the answer, so you know you've got it right. Part (b) of that question may well have been to factorise the given quadratic to get the 2 solutions for n (10 and -9), and part © was probably to reject -9 as meaningless. In that way many skills are being tested, but even if you don't get part (a) you can move on to (b) and still score some marks.

 

I didn't do much probability at school - at A level I did none at all as I sat pure maths and mechanics papers. GCSE, at least the AQA variety my kids have sat, contains a bit of everything, including basic probability.

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Actually I might be able to do it ...

 

if she had 6 orange sweets that's = 6/n

then she had 5 orange sweets = 5/n-1

 

SO

 

6/n * 5/n-1 = 1/3

 

30/n (n-1) = 1/3

 

90/n (n-1) = 0

 

n (n-1) = 90

 

n squared - n = 90

 

n squared - n - 90 =0

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i understand the forumla, what I can't see is how you are being asked to show your answer as a formula, rather than solving n and proving the formula that you were given as correct.

 

it's been years since I was at school, and they kicked me out at 15, and as I don't have kids of my own to reintroduce me to it, I'm a little rusty, but still it seems like the most practical thing to take away from this question would be an ability to actually work out how many sweets are in the bloody bag!

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Counting would achieve that.

 

that assumes that Hannah would let me near her bag of sweets, and since I pulled her hair and told her she was dumb in gym class, she hasn't been interested in sharing with me.

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  • 4 months later...

I think this is the same problem in a different form:

 

GI Joe is driving his combat hovercraft, and has come to a river which is uniformly 6m wide.

 

The hovercraft will take 0.5 seconds to cover a meter on water, and 0.4 seconds to cover a meter on land.

 

Currently GI Joe is in a safe place.

 

The next safest place is 20 meters downstream and on the other side of the river.

 

How long will it take GI Joe to get to safety if he aims his hovercraft straight across the river via the shortest crossing and then proceeds to safety along the land on the other side of the bank.

 

How long will it take him if he aims his hovercraft directly at the point of safety and drives it straight to the point of safety via the river not using the land at all.

 

If he was to minimize the time to travel to the point of safety how far downstream should be aim for, before then proceeding to it along the land on the other side of the river.

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Another one!

 

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This one is a bit harder as it involves optimising ... calculus here we come!

So where's this one from China? Seems to be about maths A level C3 standard - differentiate T(x) with respect to x, which involves application of the chain rule, and solve for dT/dx=0. Don't tell me it's a Singapore primary school entrance test or something.

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