Posted by **Sharlet** on Monday, September 13, 2010 at 6:07am.

This mystery number has 3 digits.Its digits are in the descending order. The hundreds' digit is two more than the ones' digit. If you add the 3 digit it gives you a dozen. Guess this mystery number?

- Maths -
**MathMate**, Monday, September 13, 2010 at 8:47am
If the digits are in strict descending order, then they must be [n+1]n[n-1], the sum of which is 12, i.e.

n+1 + n + n-1 = 12

Solve for n.

- Maths -
**Maths girl **, Tuesday, September 15, 2015 at 7:18am
The hundred digit is two more than the ones.

If you add three it will be 12.

Which means the hundreds is 12-3=9

To find the ones 9 - 2=7

Now we found 9_7.

To finish for sure the decending means 8

So the answer is 987.

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