byOctober 29th, 2019
How much is 12.6 × 10? This is a question from the Math Reasoning Inventory (MRI) decimal assessment. What do you think were the most common incorrect answers given by the more than 7,800 students who figured out the answer in their heads? And what about the boy who answered, “One hundred twenty and thirty-fifths?”
byOctober 25th, 2017
I taught this mental math lesson to a class of fourth graders. I chose an addition problem—99 + 17—for the students to solve mentally, purposely selecting a problem that would be accessible to the students. Also, I knew that the problem could be solved in different ways. I planned to elicit from the students strategies for figuring out the sum of 116 and then to show video clips of other students solving the same problem. After watching each video clip, we’d analyze how the student reasoned and then check back to see if anyone in our class used the same strategy.