Many of the second grade math standards are similar to the first grade standards, but they are expanded. In first grade, students add and subtract within 20. In second grade, they begin to add and subtract within 1000. In first grade, students extend the counting sequence from any number within 120. In second grade, students should be able to start at any number within 1000 and count on by ones, fives, or tens.
Grouping and then skip-counting numbers is a requisite skill for working with arrays, which we will do later in the year. Fluent skip-counters can fluidly determine the total in an an array, setting them up for multiplication in third grade.
Last week, students began to count by twos, fives, and tens to determine the number of legs, hands, and fingers in our classroom. Students approached this in different ways.
One friend went around the room, pointing to students’ legs, counting one-by-one.
Emarion grabbed a copy of the morning sign-in sheet. “I counted like this. I pointed to ‘Amy’ and said, ‘1, 2.’ Then I pointed to ‘Anna’ and said, ‘3, 4,’ until I got to all of the kids and got 48.”
Others debated that counting the total legs in the class should include those of Ms. Fay, Ms. Kimble, and me as well, which led to a conversation in which we compared strategies and totals to ensure we had all counted correctly.
When counting fingers, Karl grabbed a number line and made stacks of five, representing the five fingers on a hand. He lined up his stacks with the numbers on the number line to keep track of his total stacks. He then realized that he had only accounted for one hand, and added a second stack of five to each number. This created stacks of tens, which he counted by tens.Asanti took a pictoral approach, drawing kids and fingers. She then grouped them and counted by tens.
Phoenix set up pairs of five-stacks to represent children’s hands. She then counted by fives to find the total.
Many friends have little trouble counting by fives until 50 and counting by tens until 100. Once they get past 100, however, they are unsure how to extend the counting pattern. Similarly, they are unsure how to write three digit numbers. Upon hearing, “One-hundred-one,” many second graders write, “1001.” For one-hundred-twenty, many write, “102.” For the next two weeks, we will spend time working on grouping, counting, and writing numbers within 1000.
Learning to skip-count simply takes repeated practice. At home, our second graders will benefit from practicing skip-counting and counting by ones aloud starting at any number within 1000. Continued practice writing three digit numbers will also help immensely.