Teaching tip: Here's how I spice up the activity "Which One Doesn't Belong?"

43 because it is the only prime number

the correct answer is 16 because I like square numbers. They're so symetrical. 16 is 4 squared and 4 is 2 squared and 2 cubed is 16.

I first thought 9 is the odd one out as all the other numbers digits add up to 7. But then finding that 43 is a prime number and all the other numbers are square numbers seems more mathematical due to learned number properties.

43 doesn't belong. 3x3=9. 4x4=16. 5x5=25. The bottom right square should be 36. 6x6

9, because it's the only single-digit number, and the other numbers' digits all add up to 7.

What is a good reason to eliminate 25?

Students have mentioned that it's the only one where the last digit isn't a multiple of 3.

The other two I found are all the numbers but 25 end in a multiple of 3. And all the numbers but 16 are odd. Didn't think of the 43 is prime, love it.

9 is the only single digit & doesn't add up to 7❌ 16 is the only even number ❌ 25 is the only one that is the sum of some of the others ❌ 43 is the only prime & non-square ❌

I would go for 25 for the below reasons: Upon division on five persons each will get let’s say $5. That’s a lot of money with quite large group. Also let’s not forget they will be no fraction. That’s also count! Lastly since we don’t have a 25 bill, however there’s a $20 and a $5 coins will do the job, unlike the other numbers😀