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PostPosted: Thu Jul 26, 2012 1:45 pm 
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Joined: Mon Feb 22, 2010 2:50 pm
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Hi. Is the answer on the answer sheet wrong.

Numbers in each group are related in some way, use the rule to find the missing number.

15 (32) 2 14 (30) 2 12 ( ) 4

We get the answer as 52, but the answer given is 28 and I can't see how you would get to 28??


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PostPosted: Thu Jul 26, 2012 1:48 pm 
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Location: Buckinghamshire
15 + 15 +2 = 32

14 + 14 + 2 = 30

12 + 12 + 4 = 28

These papers have been around a long time and I can't recall there being any errors on them.


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PostPosted: Thu Jul 26, 2012 1:58 pm 
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Thanks. I can see that process now. Why is that a better method than times the 2 outer numbers together and then add the second outer number. ie: 2 x 15 + 2, 2 x 14 + 2 and then 4 x 12 + 4.

Is there a reason why the one providing the correct answer is the one to use, as this is in a standard not a multiple choice style paper. Thanks for your help!


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PostPosted: Thu Jul 26, 2012 2:08 pm 
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Location: Buckinghamshire
I see your problem now - I don't often look at the Standard Format papers. I suspect that SD's papers were originally written as Multiple Choice and then converted to Standard Format.

The question does become ambiguous in Standard Format, but my "instinct" was immediately that the two numbers in the middle are not significantly larger than those either side and therefore you are more likely to be adding rather than mulitplying.

There shouldn't be any such ambiguities on the real paper though.


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PostPosted: Thu Jul 26, 2012 2:14 pm 
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Thank you. :)


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PostPosted: Thu Jul 26, 2012 6:45 pm 
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Joined: Mon Jan 30, 2006 4:07 pm
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This one gets my children in a tizz every year

There are 3 answers, but luckily only one is on the answer sheet, the question is not be a good candidate for standard form.

15 (32) 2 14 (30) 2 12 ( ) 4

Method 1

15 x 2 = 30
add number on the right
30 + 2 = 32

14 x 2 = 28
add number on the right
28 + 2 = 30

12 x 4 = 48
add the number on the right
48 + 4= 52

Method 2

15 x 2 = 30
add 2
30 + 2 = 32

14 x 2 = 28
add 2
28 + 2 =30

12 x 4 = 48
add 2
48 + 2 = 50

Method 3

15 + 2 = 17
add number on the left
17 + 15 = 32

14 + 2 + 16
add number on the left
16 + 14 = 30

12 + 4 = 16
add number on the left
16 + 12 = 28

Patricia


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PostPosted: Thu Jul 26, 2012 7:09 pm 
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Thanks Patricia and Sally-Anne, DS had got method 1 and 2 to begin with but not 3! I generally get the standard format papers where I can as that is the format our tests will be in. It makes sense that if the papers have been converted from multiple choice ones that there may be some anomalies. I was just worried that I was missing something obvious, as to why one should be right and one wrong; so am now feeling reassured.


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PostPosted: Thu Jul 26, 2012 7:55 pm 
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Ambiguous indeed. I got 50 and DD got 52.


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