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Reeese
Sep 10, 2007, 04:21 PM
I need help with the following riddle.

I am thinking of a number between 1 and 25,000. It is a even number. The digit in the ones place is 4. The digit in the thousands place is odd. The digit in the ten thousands place is the only even prime number. If I multiply the digit in the tens place by 4, I will get 8. If I add the digit in the thousand place to the digit in the hundreds place I get 7. What is my number?

worthbeads
Sep 10, 2007, 08:37 PM
I'm going to do this step by step. I am also going to do this very fast, so ask questions if you get confused.

Steps:

1. "The ones place is 4"
We know the number has to be?? 4

2. "The thousands place is odd"
The number is one of these: ?1? 4, 3? 4, and that's all, because we can't go over 25000. (you'll see why when we get to step 3)

3."The ten-thousands is an even prime"
The only even prime number is 2, so 21? 4 or 23? 4.

4. "The tens place times 4 equals 8"
21?x4 or 23?x4, where x*4=8. We solve for x. 8/4=x 2=x, so 21?24 or 23?24.

5. "The hundreds and thousands places added together equal 7"
In 21?24 the hundreds has to be 6, so 21624. (1+6=7)
In 23?24 the hundreds has to be 4, so 23424 (3+4=7)

So the answer is either 21624 or 23424.

I get two different answers, so either I'm wrong or both answers are correct. Hopefully someone else will step in and help.

I hope I helped you some.