difficult question type

[mh1]

Need clarification on following problem-

Q: 4(22)7, 12(42)9, 6(?)7
Q: 10(14)2, 6(12)3, 4(?)4
Q: 11(13)5, 9(7)6, 13(?)7

I'm having difficulty on the above question type- have not encountered these before.

Thanks

[naga]

Need clarification on following problem-

Q: 4(22)7, 12(42)9, 6(?)7
Q: 10(14)2, 6(12)3, 4(?)4
Q: 11(13)5, 9(7)6, 13(?)7

I'm having difficulty on the above question type- have not encountered these before.

Thanks

you have to look for the relation between the two numbers before and after the brackets .

first one is 4(22)7 is 4+7=11 and 11*2=22,and 12(42) 9= 12+9=21 and 21*2=42,
and 6+7=13 and 13*2=26.

similarly 10(14)2,6(12)3,4( )4.

in this 10+2=12 then add 2,6+3=9 then add 3 so the last one will be 4+4=8 then add 4 .so the answer must be 12.


finally 11(13)5,9(7)6,13( )7
we have to subtract 11-5=6,then multiply by 2and add 1,6*2+1=13
and 9-6=3,3*2=6+1=7,
13-7=6,6*2=12+1=13.

so it must be 13.

[Y]

I saved this text from a message posted by a Guest, Hilda, last year. The guidance is invaluable. If the answer doesn't leap out immediately - or the one that did leap out proved to be wrong! - the child needs to work systematically through the options without panicking.

Y

Posted: Wed May 02, 2007 8:08 pm Post subject:

________________________________________
Patricia has a tip for these bracket maths somewhere. Hopefully she'll drop in and post the link.##Basically many of the questions involve two operations. So always try

Operation 1 = + ,- ,X, or, / (divide) the outside nos ; then
operation 2 = +, -, X or / by an integer, or by either the left or right outside number

So if you are stumped always try each of the 4 possibles in operation 1, then ask yourself which operation 2 would you need to do to get to the middle number. Does it work for both examples. If yes you've got it.

So in the present case:
operation 1 = - (subtract the outside numbers - smallest from largest) then
operation 2 you can work out to be + an integer, in this case 10. It works for both so it must be right.

Genrally when you've done lots the anwsers leap out at you (honestly they do after enough practice) so you don't have to go through all the possible operations 1 and 2. But it is useful to have this as a technique to fall back on when you are stumped. My 10 year old got used to doing it, and in a set of 6 questions of this type, there was usually one tricky one he needed to use it for. Good luck. Hope this makes sense.

[mh1]

Thank you Y and Naga very useful information