Help with VR GL pack 2 test 5 Q 41

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janet71
Posts: 166
Joined: Thu Feb 02, 2012 3:12 pm

Help with VR GL pack 2 test 5 Q 41

Post by janet71 »

Help with VR GL pack 2 test 5 Q 41

4 (12) 36
2 (6) 18
5 (?) 45

answer is 15 but can not see why

I can see that all the numbers in brackets and the right hand number are the result of x3 but thats about it. Any help as its stumped both me and DS
Reading Mum
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Location: Reading

Re: Help with VR GL pack 2 test 5 Q 41

Post by Reading Mum »

that looks a dodgy one, missing number is 3 x left or 1/3rd of right. I thought you were supposed use both left and right to drive the missing one.
janet71
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Joined: Thu Feb 02, 2012 3:12 pm

Re: Help with VR GL pack 2 test 5 Q 41

Post by janet71 »

Reading Mum wrote:that looks a dodgy one, missing number is 3 x left or 1/3rd of right. I thought you were supposed use both left and right to drive the missing one.
Me too and Im sure you do but wondered if this was an error on the paper
DC17C
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Joined: Wed Oct 12, 2011 9:34 pm

Re: Help with VR GL pack 2 test 5 Q 41

Post by DC17C »

4 x 6 =24 36-24= 12
2 x6 = 12 18-12= 6
5x6 = 30 45 -30 =15

- tricky one took a while to get my head around!
janet71
Posts: 166
Joined: Thu Feb 02, 2012 3:12 pm

Re: Help with VR GL pack 2 test 5 Q 41

Post by janet71 »

janet71 wrote:
Reading Mum wrote:that looks a dodgy one, missing number is 3 x left or 1/3rd of right. I thought you were supposed use both left and right to drive the missing one.
Me too and Im sure you do but wondered if this was an error on the paper
cheers :D
Hera
Posts: 856
Joined: Mon Feb 22, 2010 3:50 pm

Re: Help with VR GL pack 2 test 5 Q 41

Post by Hera »

I would have worked that out as:

3x4=12, 3x12=36
3x2=6, 3x6=18
3x5=15,3x15=45

So the missing number is 15
justkeepswimming
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Joined: Thu May 31, 2012 2:10 pm

Re: Help with VR GL pack 2 test 5 Q 41

Post by justkeepswimming »

Or...

4 x 36 = 144 144=12x12
2x18 =36 36 = 6x6
5x45=225 225=15x15

Somewhere (one of Patricia's posts I think) I read some advice that you should always start by either + - x or / the two numbers outside the brackets first and then see how you might get from there to the number in the middle....have found this a good way to help my dd. The above is tricky I thinkbut I guess children might be expected to recognise 144 and 36 as square numbers?
bristolmum
Posts: 32
Joined: Tue Apr 10, 2012 5:48 pm

Re: Help with VR GL pack 2 test 5 Q 41

Post by bristolmum »

Question to Patricia may be.


My DS had a different approach, he worked out his answer like this:

4X5 = 20 20+4 = 24 36-24=12
2x5= 10 10+2 = 12 18-12=6
5x5 = 25 25+5 = 30 45-30 = 15

Pls comment if he's approach is alright.
Bm
christmasbonus
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Re: Help with VR GL pack 2 test 5 Q 41

Post by christmasbonus »

My working out was possibly more bizarre - I multiplied the first number by 9 to get the last number, then divided by 3 to get the middle number. Slightly different way of working it out, but I have tried my version with other questions that come up here and it always seems to work (tho' possibly I am over-complicating things).
StacatoMum
Posts: 26
Joined: Tue Feb 21, 2012 6:44 pm

Re: Help with VR GL pack 2 test 5 Q 41

Post by StacatoMum »

janet71 wrote:Help with VR GL pack 2 test 5 Q 41

4 (12) 36
2 (6) 18
5 (?) 45

answer is 15 but can not see why

I can see that all the numbers in brackets and the right hand number are the result of x3 but thats about it. Any help as its stumped both me and DS
This is how I would approach this question. Looking at the differences there are big gaps between the sets so I considered that there might be a division somewhere. I also noticed that the last numbers are divisible by 9.

4X2= 8 ; 36/9=4; 8+4=12
2X2= 4; 18/9=2; 4+2= 6
5X2=10; 45/9=5; 10+5 =15

Hope this helps.

StacatoMum
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