## Tuesday, February 12, 2008

### Time for a Special Valentine Challenge!

Anyone interested in a little critical thinking? In honor of Valentine's Day, I am adding a special little math activity. Who doesn't love a little critical thinking? I find myself hooked on these puzzles, as I'm sure you will too.

These logic puzzles, also known as logic grid puzzles, require you to carefully read and analyze the given clues many times in order to solve them. You are trying to figure out who goes with what (or in the example below, who did each person get a Valentine's Day card from). Your job is to eliminate the impossibilities. The easiest way to solve these problems is to create a square chart. Let's look at a quick sample below.

Jonathan, Jacob, Devin, and Kevin each gave one Valentine's Day card to a girl in their class. The girls Kylie, Ashley, Alexis, and Mackenzie each received one Valentine's Day card and want to know who gave it to them.

Clues:
1. Jacob could not decide whether to give a card to Ashley or to Kylie. They are both nice, and he likes to talk to both of them. Since he couldn't decide, he decided to give a card to someone else on Valentine's Day!
2. Ashley knows that either Jacob or Kevin gave her a card.
3. Devin gave Mackenzie a card.
To solve this problem, create a square chart. (Most websites create them for you.) Go through the clues one at a time. Cross off the people on the chart as you eliminate them by putting an X in their square. After reading only the first clue, this is what I learned:

Jacob did not give a card to Kylie or Ashley, so I placed an X beside Jacob's name and under Kylie and Ashley. This doesn't tell us too much yet, but this information will be important soon.

After reading the second clue, I learned that either Jacob or Kevin gave Ashley a card. Since, in step one, we learned that Jacob did not give Ashley a card, her card had to have come from Kevin. Any symbol can be put in the "yes" spot. I used a heart. Popular symbols include happy faces and check marks. This also tells us that if Kevin gave the card to Ashley, he couldn't have given a card to anyone else. Also, Ashley couldn't have received a card from anyone else.

The last clue gives me everything I need to solve this puzzle. (If it did not, I would have had to reread all of the clues.)
By finding out that Devin gave Mackenzie a card, we can cross off everyone else on Devin's row and Mackenzie's column. It also means that the only person left for Jonathan to give a card to is Ashley. The only person for Jacob to give a card to is Alexis. Puzzle solved!

Want to try your hand at a few puzzles?
Level: Easy
Level: Medium
Level: Hard
And for the parents that can't get enough of them, here is a site just for you. If you are a member of edHelper website, they have a lot of great puzzles as well.