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PostPosted: Fri Jun 10, 2016 5:46 pm 
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Place the numbers 1 to 9 inclusive, one each, in these gaps to make this sum correct:

- - - - x 3 = - - - - -


Any help with how to approach this question (and the answer) would be greatly received. There just seem to be too many possible combinations to trial and error this, so I must be missing something!


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PostPosted: Fri Jun 10, 2016 9:45 pm 
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I haven't had a go at it myself, but the first thing to bear in mind is that the sum of the digits making the answer has to be divisible by 3 (from divisibility rules).

Also, the answer has to be less than 30,000 because 30,000 divided by 3 is a 5-digit number and you need to multiply a 4-digit number by 3 to get a 5-digit number answer. This means that the first digit in the answer cannot be bigger than 2 and that should give you a clue as to what digit the first number may be starting with.

(x-posted with Guest55 :) )

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Last edited by PurpleDuck on Fri Jun 10, 2016 9:58 pm, edited 2 times in total.

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PostPosted: Fri Jun 10, 2016 9:50 pm 
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Start with the units digit on the left - are there some numbers you can eliminate?


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PostPosted: Fri Jun 10, 2016 9:54 pm 
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5832*3=17496


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PostPosted: Fri Jun 10, 2016 9:58 pm 
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Sorry - 'see' - what is the point of posting an answer? This does not help the OP at all :cry:


Last edited by Guest55 on Fri Jun 10, 2016 10:00 pm, edited 1 time in total.

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PostPosted: Fri Jun 10, 2016 10:00 pm 
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See - you've just taken away Jaxx's entertainment for the weekend...

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PostPosted: Fri Jun 10, 2016 10:55 pm 
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I too got the same answer as above. I focussed on 5 first. Since 5x3=15 and we cannot have two fives, I thought that perhaps 5 was a part of the 4 digit number. It might then have got a carry over of 1 or 2 from the previous number changing the multiplication so that the answer would no longer have a 5 in it. Also it was no use having 51,52 or 53 as they were not providing a carry over of 1 or 2.
51x3=153, 52x3=156, 53x3=159.
So the number after 5 needed to be 4 or more.
example: 54x3=162
Then I wrote down the remaining digits and picked the ones that satisfied the 3x table rule. I inserted them at the end of the 3 digit answer (above) to make it a 5-digit number and see if it worked. From this point it was trial and improvement I am afraid.

It did take me a while. How are the children expected to do this in a short amount of time I wonder.


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PostPosted: Sat Jun 11, 2016 7:58 pm 
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Its another answer 5823*3=17469 we can inter change 2 and 3 because that multiple 3 have no carry


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PostPosted: Sat Jun 11, 2016 8:29 pm 
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Please stop posting answers and explain how to tackle the question.

Answers don't help someone tackle a similar question in the future.


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