Today I was working with one of my students who acts a lot dumber than I really think he is. We were going over the concept of addition with regrouping. He had drawn a picture which showed 7 ones and 6 ones being added in the ones column. He had moved all 13 ones down to the ones' answer spot.
I told him that there were too many ones to go there and that we needed to regroup. So I asked him how many ones we needed to put together to make a ten.
His reply: Five?
I said, "Think about the name of the place value. It's the TENS place. How many ones do we need to make a TEN?"
With more certainty this time, he answered, "Three."
I finally went and grabbed the base-ten blocks, which we had worked extensively with yesterday, to show him that three ones actually did not make a TEN.