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westworld
Average Member

USA
19 Posts

Posted - 04/04/2012 : 22:46:58

Jordan, Justin and Jeff are brothers whose ages are 29, 30 and 31 (in any order). Your job is to determine the brothers' ages from the clues below. There's one catch though....only ONE clue is true. The rest are false. Good luck!

1. Justin is 30.
2. Jordan is the youngest.
3. Jordan is 31.
4. Justin is one year older and one year younger than his brothers.
5. Justin is not the youngest.
6. Jordan is not two years older than Justin.
7. Justin is the oldest.
8. Jeff is older than Jordan.

someguy
Advanced Member

Canada
130 Posts

Posted - 04/07/2012 : 15:15:14

All you really need to do to answer this one is try it.
You just need a systematic way to proceed.

What are the possible ages of Jordan, Justin, and Jeff?
There are only 6 possiblilities.

1) Justin is 29, Jordan is 30, Jeff is 31
2) Justin is 29, Jeff is 30, Jordan is 31
3) Jordan is 29, Justin is 30, Jeff is 31
4) Jordan is 29, Jeff is 30, Justin is 31
5) Jeff is 29, Justin is 30, Jordan is 31
6) Jeff is 29, Jordan is 30, Justin is 31

For each possibility, check to see how many of the statements are true.

Note: with a little thought, you can make it even easier.
Statement 4 implies statement 5
If Justin is the middle child, then Justin is not the youngest.
Justin can't be the middle child.

Statement 7 implies statement 5
If Justin is the oldest, then Justin is not the youngest.
Justin can't be the oldest.

Justin is the youngest of the three brothers.

You only need to consider the following two possibilities.
1) Justin is 29, Jordan is 30, Jeff is 31
2) Justin is 29, Jeff is 30, Jordan is 31

I will leave it up to you to figure out which of these is true (just check the list of clues and see which leads to exactly one clue being true).

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