carol made a ten to subtract from 15. she got an answer of 10. is carol correct? explain
Reasonableness second grade math
Of course not. Observe:
15
-10
-----
5
You subtract 0 from 5, leaving 5 in the ones position. Then,
you subtract 1 from 1, leaving zero in the tens position.
If you have the misfortune of having Common Core shoved
down your throat, this will be marked wrong. You will be expected
to "know" that you are supposed to add 27 to both numbers and
then subtract. You will never be taught to do math the intelligent
way, the way it has been done for hundreds of years, the way that
has created bridges, skyscrapers, airplanes and spacestations.