Math automaticity- decomposing numbers to 10
Lesson
Grade 2
General
Students learn to decompose the numbers 2-9 as quickly as possible.
Relevance
It is useful to be able to quickly decompose numbers so you can quickly split a number. If you have 5 children and 2 want a popsicle you will quickly know that you need 3 more.
Introduction
Students practice decomposing the ducks waiting by the canal. Drag the ducks onto the picture of the canal. Then practice decomposing the balloons, which are different colors, and tulips, which are the same color. Ask students how to decompose and be aware that some students will already be able to decompose without counting or in their heads.
Development
During the instruction all the numbers from 2 to 9 are shown in addition to their numbers and represented in green beads. Discuss that the numbers in a number bond can always be switched and show students how this works. Say that in class we're going to try decomposing numbers as quickly as possible. Use the hourglass to encourage students to quickly give their answers. Students are given 3 seconds per decomposition. If more time is needed (or less) the time can be modified.
Check that students understood quickly decomposing numbers 2-9 by asking the following questions:
- What is decomposing a number?
- How can you decompose as quickly as possible?
- Decompose the number 8. 2 and... How did you figure this out?
Check that students understood quickly decomposing numbers 2-9 by asking the following questions:
- What is decomposing a number?
- How can you decompose as quickly as possible?
- Decompose the number 8. 2 and... How did you figure this out?
Guided Practice
Students get a set of a number that is decomposed in 5 ways. Students are asked to complete the missing number as quickly as possible. The timer in the exercise counts up in time and students try to match the target time.
Closing
Emphasize that it is important to be able to quickly decompose numbers if you need to quickly know how many you miss of something or still need of something. Ask students to come up with examples of these situations. Then practice with decomposing the three given numbers as quickly as possible to check that students are able to quickly decompose numbers 2-9.
Teaching Tip
Students who have difficulty can be supported by first writing down all the number bond charts of 2-9 showing all possible decompositions and using these during the lesson. If students still have difficulty with decomposing, they can be supported by the use of manipulatives to visualize the decomposition.
Instruction materials
blocks