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# 777 maths problem

Thu 10 May, 2012 10:47 pm
using all digits 1-9, what three 3 digit numbers add up to 777 ?
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engineer

1
Thu 10 May, 2012 11:37 pm
@nicoleg,
The digits 1-9 add up to 45 and 3x7=21. For every number "carried" you increase one place by one and decrease another by ten so a net -9 meaning you can get combinations that add up to 36 or 27 or 18 or 9 but not 21 so this is not possible.

Example 145, 267, 398 = 810 adds up to 9.
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contrex

1
Fri 11 May, 2012 12:06 am
Engineer, I think, in your haste to asnwer, you answered a different question from the one that was asked.
contrex

1
Fri 11 May, 2012 12:12 am
There are many sets of 3 three-digit numbers that add up to 777. Is the question "how to calculate how many"?

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markr

1
Fri 11 May, 2012 08:59 am
@contrex,
Nope - he was spot on: "using all digits 1-9"

The digital root of the sum of any set of numbers made up of the digits 1-9 (used once each) will be 9 (or 0). The digital root of 777 is 3.
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