Who’s good at maths?!

[Rory]

Hi there

We are struggling with this question, does anyone have any thoughts??

Thanks
Rory

Attachment 18514


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[Rory]

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[ryanb741]

230cm and 184 cm

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[Rory]

230cm and 184 cm

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Unless I’m being very dense, I’m guessing that was a joke! If not, what’s the key to working it out??

Cheers
Rory


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[Kingstepper]

He’s correct!

[ryanb741]

Unless I’m being very dense, I’m guessing that was a joke! If not, what’s the key to working it out??

Cheers
Rory


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The picture was a visual trick to shake you off the scent. In reality the missing part that applies to both A and B was much bigger.



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[Rory]

Thanks Ryan, that’s the bit we are struggling with - how to determine the size of the gap!

Cheers
Rory


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[Mr Pointy]

Call the overlap X.
A - X = 90 so A - 90 = X
B - X = 44 so B - 44 = X

So A - 90 = B - 44
And A - B = 90 - 44 = 46

But B = 0.8A

So A - 0.8A = 46 so 0.2 A = 46 & A = 46/0.2 = 230
B = 0.8A = 184

[markc]

A=230 and B=184 is correct...

A+44 = B+90

also 0.8xA = B

thus A+44 = 0.8A+90

solving...
0.2A = 46

so A = 230

B = 0.8 x 230 = 184

simples.

Cheers,
Mark C

[Rory]

Thanks so much everyone. I’m going to be in real trouble once my son is in secondary school!

Cheers
Rory


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[Halitosis]

That's a primary school question? If so then my opinion of my own maths skills definitely needs re-calibrating

[vagabond]

I bet that's an 11+ exam question?

Remember doing similar with both my daughters when they sat 11+, now 21 and 19, so going back a few years, though maths is maths.

[Rory]

Yep my son turned 11 this week and is in his last year of Primary.

Cheers
Rory


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[Kirk280]

My wife had to work it out for me. I hate maths when numbers are missing! 🤣

[Chinese_Alan]

Massively overthought that but got there in the end, jeez.

[Ax]

Don't know how you're supposed to do it nowadays but for me this is the easiest way to look at it :
(90 + x) * 0,8 = 44 + x

[Kingstepper]

Don't know how you're supposed to do it nowadays but for me this is the easiest way to look at it :
(90 + x) * 0,8 = 44 + x

How I would have done it too.

[100thmonkey]

Carol Vorderman

[swisstony]

The question is designed to confuse and took me a while to see it...

Simplest way (without using the greek alphabet) is to slide B to the left by 90 cm... the gap is then 44-90= 46.. which is 20% of A.

A is 5*46 = 230
B is 4*46 = 184

[Brighty]

Seemed fairly straight forward to me, dunno about 11yr olds though

Both top and bottom are the same total length, so

A+44=B+90

Rearrange that to got

A-B=90-44=46

We know that B is 80% of A, so A-B = 20% =46
A=46/0.2=230
B=230-46=184

[tixntox]

Maths and MAFs. PITA
https://www.youtube.com/watch?v=MrCPIrs90eg

[GraniteQuarry]

I see dead people.

[amnesia]

Don't know how you're supposed to do it nowadays but for me this is the easiest way to look at it :
(90 + x) * 0,8 = 44 + x

That's what I did too...

44+X = (90+X) x 0.8

[hops]

Even with answers I have no idea!

[Chinese_Alan]

Did think when working out I wish I was being taught this in class with loads of others to answer afterwards.

[PickleB]

The question is designed to confuse and took me a while to see it...

Simplest way (without using the greek alphabet) is to slide B to the left by 90 cm... the gap is then 44-90= 46.. which is 20% of A.

A is 5*46 = 230
B is 4*46 = 184

I don't think it's "designed to confuse", just very poorly formulated / worded.

"Find the length of each rectangle"...which is the length when we have no information about the other sides?

Why introduce rectanglea when the question is about uni-simensional lines?

OK, maybe it's not 'designed' to confuse but it's design is certainly confusing.

[catch21]

It’s hopeless. I’ve been doing private maths tuition for 20 years. It’s not about 284 or 583 or 17 and a half, it’s about how you approach a problem like this. A lot of primary age kids will close their eyes, screw their face up and try to come up with a number!

What I do straight away with a new student (I have the luxury of doing 1:1 not 1:30) is leave a pad of paper and pencil in front of them (and one in front of me too) and see how long it is before they pick the pencil up.

What I’d do with this, if you’re struggling, is to pick up a pencil and draw your own version of it. That’s a good start.

[Kingstepper]

I don't think it's "designed to confuse", just very poorly formulated / worded.

"Find the length of each rectangle"...which is the length when we have no information about the other sides?

Why introduce rectanglea when the question is about uni-simensional lines?

OK, maybe it's not 'designed' to confuse but it's design is certainly confusing.

Not sure about that. Easier to picture the problem with rectangles than with 2 overlapping lines. Just my opinion anyway.

[David_D]

Did manage it but suspect I wouldn't have done at primary school!!

[PickleB]

Not sure about that. Easier to picture the problem with rectangles than with 2 overlapping lines. Just my opinion anyway.

Yep...I'm fortunate that two overlapping lines wouldn't confuse me. Two rectangles had me looking for areas...until I read the question through properly.

To my mind the question setter might have used 'the overlapping sides' rather than 'lengths' as there was no reference for the breadth. But then we're getting into Plain English rather than geometry...except that this question had nothing to do with geometry, it was simply algebra.