Challenges for the mathematically challenged?

[Harald]

(12-18-2022 03:11 AM)Allen Wrote:  The best I've found is Project Euler. Mos, if not all of the first 20 problems can be done on a HP calculator.

That looks interesting.
Is there anything like it at a much more basic level?
My youngest son is 5 years old now and not in school yet. He is asking me to give him mathematical challenges almost every day. His level now exceeds the second grade math his older sister is currently doing.
I am worried he will get bored as school, but I still would like to feed his curiosity. Any recommendations?

He sometimes surprises me. When he was three my wife was discussing a dice with my daughter. The question was how many corners does a dice have. She said 6. And was corrected it has six sides. A bit of guessing followed. Then from the background a little voice was raised, looking up from the toys "oh come on, it's 8!"

A couple of days ago I asked what is the middle between the largest two digit number and smallest one digit number.
I was thinking he would take one as the smallest one digit number. He was silent for a while. Then said "that doesn't work", 99 is odd. While discussing why it didn't work it became clear he used 0 as the smallest one digit number and so wanted to divide 99 by two. A few seconds later it became clear to him he wasn't limited to natural numbers and argued "if it was apples,I could cut one in half. So 49 and a half"

I have only his sister to compare with, but to me that seemed like an awful lot of thinking for a 5 year old.

Cheers,
Harald