Regarding the original question, it was shit. If my child was marked down for that I would complain to the teacher. The teacher's remark seemed snide to me, too. Sometimes we add things that aren't sets, and can't be broken down into smaller sets. There were no units on 8 and 5. What if they were battery voltages?
The question did not convey that making 10 was one step along the way to getting the actual answer. Instead, it implied that 8 + 5 actually was 10, which is incorrect and confusing.
Having said that, applying a strategy of breaking math questions down into simpler math questions is very important.
Instead of coming up with these funky ass meaningless questions, they should be teaching these kids something useful. If they can add, why do this funky ass "make ten" shit? Just do the usual order. Teach them multiplication... then algebra next. Then teach them trig and calc.
Imagine how difficult it's going to be on these kids in Calc 2 trying to, "make ten" when the problem calls for derivatives.
What Blackened doesn't appear to understand is that this arithmetic strategy IS based on algebraic principles.
Think of it like this:
8 + 5 = X
8 + (2 + 3) = X
(8 + 2) + 3 = X
10 + 3 = X
13 = X
We substitute (2 + 3) into the equation in place of 5, and it works because they are equivalent. Equivalence is a very important concept for algebra. Students are also learning to apply the commutative property of addition (without even knowing it).
As other posters have mentioned, a lot of us figured out how to do this on our own. However, it is something that everyone should learn. By using these techniques, students improve their numeracy, and are more capable of solving complicated arithmetic because they see how to break it down into a few simple steps instead of having to do one big complicated step.
Really, the standard methods try to do the same thing. It's standard for students to learn to add different place values separately, and then combine the answers. However, that isn't always the most efficient approach.
Example: 53 + 99
Standard:
53 + 99 = X
((5 + 9) x 10) + (3 + 9) = X
(14 x 10) + (12) = X
140 + 12 = X
152 = X
By contrast:
53 + 99 = X
(53 - 1 ) + (99 + 1) = X (making 100s)
52 + 100 = X
152 = X
I think it's important to teach this type of strategy as an option, and I understand that it utilizes algebraic principles which will make the students BETTER prepared for algebra. However, I think it's important to ultimately let the students decide how they want to do simple arithmetic (and any math problem for that matter) as long as the approach is sound.