Mm, it doesn't sound like the parents "can't do math", it sounds like they aren't familiar with the algorithms and methods being taught these days.
I haven't taken the time to understand the new methods, but just from the names I get the feeling it's more like the methods I "natively" used to do multiplication and division very quickly in my head when I was a child (under 12).
My methods for both division and multiplication involved breaking the numbers into easy parts. For instance, if I had to multiply 16x7, I'd split it into (16x5) + (16x2). 16x5 I'd use a quick rule that it is the same as 1/2 of (the first number x 10), or just (half of the first number times 10). Multiplying something by 2, 3 or 4 is always easy, so even if it was like 12.3 x 47, it always works. For the latter, I'd so something like (12.3x50)-(12.3x3) since multiplying something by 50 (broken into (X5)10) is always easy, for instance.
For division, I'd do something similar, finding the nearest easy number, and then iteratively working on the difference. For instance, to divide 412 by 17, I'd start by saying 17x10 is 170, and that times two is 340, so we have 20 plus (the difference between 412 and 340, divided by 17). Then, I'd take an easy block of that, like 17x2, and see that we have 17x2=34, so you have 4 times and a remainder of 4. So, my answer would be 24 and a remainder of 4.
Of course, teachers didn't want to see this. The most boring and damaging teachers would insist that I use the standard 'long division' algorithm, though I could do division like this faster in my head than most kids could do it on paper. Of course, that method is valuable too, and necessary for more tricky problems, but the discouragement of my natural intuition didn't help at all.
In fact, in this case (412 divided by 17) what you did is exactly what the long division algorithm would have you do -- try to divide 41/17, which is really 410/17, and take the closest-without-going-over multiple of 10 -- 20 in this case, then recognize how much you actually "used up" -- 340 -- and then divide into what's left.
So it's even worse than you imagined with your ignorant teachers -- you were doing long division after all and they didn't recognize it.
I haven't taken the time to understand the new methods, but just from the names I get the feeling it's more like the methods I "natively" used to do multiplication and division very quickly in my head when I was a child (under 12).
My methods for both division and multiplication involved breaking the numbers into easy parts. For instance, if I had to multiply 16x7, I'd split it into (16x5) + (16x2). 16x5 I'd use a quick rule that it is the same as 1/2 of (the first number x 10), or just (half of the first number times 10). Multiplying something by 2, 3 or 4 is always easy, so even if it was like 12.3 x 47, it always works. For the latter, I'd so something like (12.3x50)-(12.3x3) since multiplying something by 50 (broken into (X5)10) is always easy, for instance.
For division, I'd do something similar, finding the nearest easy number, and then iteratively working on the difference. For instance, to divide 412 by 17, I'd start by saying 17x10 is 170, and that times two is 340, so we have 20 plus (the difference between 412 and 340, divided by 17). Then, I'd take an easy block of that, like 17x2, and see that we have 17x2=34, so you have 4 times and a remainder of 4. So, my answer would be 24 and a remainder of 4.
Of course, teachers didn't want to see this. The most boring and damaging teachers would insist that I use the standard 'long division' algorithm, though I could do division like this faster in my head than most kids could do it on paper. Of course, that method is valuable too, and necessary for more tricky problems, but the discouragement of my natural intuition didn't help at all.