Too me check your work doesn't mean all the time redoing the problem...if it was long division I check by multiplying, if it is an equation, I might plug the answer in to the original question....I might check by estimating and see if my answer is reasonable...like 20% of a number and my answer is bigger than my number I know I have done something wrong.
And sometimes I just spot check random problems by redoing them. But I did not and do not expect my son to do every problem twice. No one is perfect, go through slowly and carefully the first time and with a minimum of checking what you produce should be good enough.
And the US Dept of education says that 3 to 5 problems done correctly is the optimal number of practice problems...so if you have 3 different types of problems for one concept then your homework should be 9-15 problems long.
