General Discussion
In reply to the discussion: How would you answer this test question? From a 1st grade Common Core test. [View all]callous taoboy
(4,767 posts)you've taught them to turn the bottom number into a "hundred" number.
932 - 687 becomes 945 - 700 = 245. Mental math. But that type of problem / lesson comes later, in third grade. Second grade we start with tens: I'll soon be teaching them to turn the bottom number into a "ten" number: e.g. 44 - 28 = 46 - 30. We will have used the 100s chart so much by then, subtracting multiples of 10 from given numbers via games and such, that 16 will be the ready answer. Can you do that in your head? Can you visualize 46 - 30 on a hundreds board? It is still hard for me since I was taught "old school." I will be instructing them to "see" the 100s chart by then, or will allow my slower learners to use the 100s chart with a plastic chip each time to derive the answer until it becomes natural. Mental math is the only true way to flex the math muscle in the brain and free oneself from bulky algorithms. However, since the test may ask them "regrouping" questions, I will also be teaching them "old school" methods as I call them. Some of my students will prefer that method and that is o.k.