i'd agree with the teacher that this is the most 'mathy' way of getting a kid to do a multi problem worksheet i think it would have been kinder to to do 123 an

i'd agree with the teacher that this is the most 'mathy' way of getting a kid to do a multi problem worksheet i think it would have been kinder to to do 123 and 900 while also offering the possibility of choosing that it is impossible to achieve i also disagree with the op's tactic of 'proving' this this attempt to do less work to show the impossibility of the problem furthers the math education fallacy that numbers are material stead an abstraction his method would falter in any other base in research this reasoning is great at limiting a problem's scope but is useless as evidence in a proof, for instance: primes must end in 1,3,7, or 9, but to say any number ending in those digits is prime is clearly false..also 2,5 :p i like the question the teacher offered but i think it is more appropriate in the math education i have been touting as the necessary future: teach the student to write a program that builds every possible iteration, adds them, then sorts the sums, then search for your desired value learning math and programming together it's long time to free our thoughts from rote arithmetic so we can think about larger implications and further abstractions more readily i find it difficult to accept that the teacher truly just moved on without discussing this problem, that reads more as an excuse to write this post, but if it is true that is a ridiculous failure on the part of the teacher also, offer kids real open questions stead some trick question, when i was in school i used to say to my math teachers 'why should i do these problems? you already know the answers' they treated me like a jerk, now that mindset is how i direct my research