On a remote (imaginary) island, there are 11 snakes and a single mouse. As you’d expect, snakes eat the mice. But contrary to what you’d expect, when a snake eats a mouse, it turns into one.
The snakes live by only two rules:
1. Don’t get eaten.
2. Eat mice as long as rule #1 isn’t violated.
How many snakes and mice will there be left on the island?
My family sings Christmas carols at the hospital where my wife works.
We do this every year and since we started, have not missed a single year.
The next time we do this will be the 18th consecutive Christmas.
My 15 year old daughter has been every time.
She was born in March 1999 so the first year she came was December 1999 (before her 1st birthday).
Her first time was when she was 0, second time when she was 1, third time when she was 2, etc…
Now that she is 15, she has been 16 times. Oh and of course she was also present in December 1998 in her mum’s belly, due to be born the next March.
So, a total of 17 times and next time will be the 18th.
Thanks to Michael for submitting this real-life brain teaser about his family.
A similar problem can be found in L.A. Graham’s Ingenious Mathematical Problems and Methods with a range of 1 to 9, but the principle remains the same – the numbers with the smallest difference produce the largest product. You start out with the highest two digits, 7 and 6, then attach 5 and 4, putting the smaller of the two digits with the larger number, giving you 74 and 65. The next two highest digits are 3 and 2, giving you 742 and 653. Finally, you add the 1 to the lower number. Page 80 has the details of that solution.