Wow, am I actually publishing a blog post for the first time in a long time? It took Halloween to motivate me! Of course by now I'm sure I've lost my readership but if you happen to come across this...

As posted on twitter. com/dmarain a few minutes ago, here is a challenge for your 4th graders and above...

We may choose to call 13 & 31 a '2-digit distinct prime reversal pair'. (This means I invented that name because it's my blog!)

The challenge is to list the other 3 such pairs in 31 sec or less! Of course you could argue for a 4th pair...

And, yes, I realize this is not a brand-new original problem. In fact I published a question like this before.

REFLECTIONS...

Do you think there is there any benefit to a problem like this?

Could a variation appear on a standardized test or SAT/PSAT?

Instead of racking your brain to invent more like these for your students why not ask each group of students to come up with a couple to stump their classmates! You could also look up 'primes' in my topics list in the sidebar and you'll find a few more...

NOTE: I don't usually post answers in my blog figuring that one of my commenters will do so.

## 2 comments:

good question! I think a good hint might be to ask which sets of 10 would we eliminate from our lists. Ex: since no double digit prime can end in 2, none of the 20s primes can be considered.

Good hint, Jameel. I'm a huge believer in withholding hints for awhile. We would like youngsters to draw the conclusion that the tens' digit cannot be even or a '5' but we know some groups would need more promoting. I'd rather err on saying less! Afterwards these would be great discussion points for developing conceptual understanding.

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