Hero Zero and the Mental Math Mystery
During calendar time, we are counting the days of school until Hundred's Day. We have a raccoon puppet with a cape and mask named Hero Zero who visits every time our number has a zero in the ones place. Students love to anticipate when he will come next and often count up to the next "Hero Zero Day."
Students have been using a variety of tools in the classroom to figure out when that next "zero" day will be such as the ten frame, the number line or grid, a bead string, or their fingers. With all our work with sums of 10, it is exciting to see many students using mental math skills to solve the problem and not need to use tools.
Another skill we have been working on is counting by tens starting at any number. We practice this during calendar, math class, and throughout the day.
Now every few days during calendar, we figure out how many more days until Hundred's Day. Many students can figure this out quickly when we are on a "tens" number such as 50 or 60.
Choosing a number like 64 can be a mystery. Hero Zero can be quite a motivator in this mental math mystery. The students know that on Hundred's Day, Hero Zero will be doing something special with a magician named Captain Hundred so they are eager to figure how many days until Hundred's Day.
When we were on Day 64, I posed the question, "How many more days until Hundred's Day?" It was fun to watch two students explain their strategy.
Student #1 used his knowledge of sums of 10 first and said, "I know 64 and 6 more is 70 because 4 and 6 is 10. Then I counted by tens to 100 and that is 30. The answer is 36."
Student #2 used her knowledge of counting by tens first and said, "I started at 64 and counted by tens and said 74, 84, 94 and knew that was 30. Then I knew 94 and 6 more is 100. So the answer is 36."
I showed the students what that looks like on an empty number line so they could visualize it. We also did it on our hundred bead string for another visual model.
With all our explorations with numbers, I'm hoping to take the mystery out of mental math for all my students.