Lesson 9: Numbers 20–50
Lesson Objectives
- Count orally to 50
- Count on from any number
- Associate the number of objects with the numeral
- Represent numbers with pictures
- Use numerals as abstract representations of numbers
Materials
- Extend Workbook (Page 9)
- 100s Chart
- Highlighters, crayons, coloring pencils, or markers
- Linking cube manipulatives or other stacking manipulatives (to total 16-19)
- Beads and strings
- Place value mats
- Whiteboard with dry erase markers and erasers
- Straws and rubber bands (optional)
Step 1: Warm Up (5 min)
Practice skip counting by five using a hundred chart. Practice counting with student ages as a starting number, adding 10 to each number in sequence. Practice throwing a ball in a group, counting from a given number. Practice counting aloud from a given number to a given number of steps.
Step 2: Vocab Review (5 min)
Count on, sequence
Step 3: Model (5 min)
Pull out a 100s chart and have students highlight or color in all tens (10, 20, 30) for support. Take your linking cubes, beads and strings, or straws and rubber bands and work through grouping two groups of 10 to make 20, then add in extra objects to represent numbers 21-29. Continue making more sets of 10 and adding in ones to make larger numbers up to 50 (28, 35, 42. Draw a group of 10 (e.g. stars) on a white board and circle the group of 10. Then draw 6 stars outside of the circle to represent 16, and then another star to represent 17.
Step 4: Guided Practice (5 min)
Tell students that they have represented numbers over 19 in many ways, and they all show the place value of the number. It is 10 objects, or 1 bundle of 10 and ones on the place value chart. It is a two-digit number: tens and ones. Give students different manipulatives to play around with and work with students to make bundles of 10 (e.g. 10, 20, 30, 40, 50), then a bundle of 10 with so many extra to make numbers 20-50. Students may also use white boards and draw groups 10, circling the group and making so many extra outside of the circle to represent numbers 20-50.
Step 5: Student Practice (5 min)
Go to Student Workbook Page (9). Tell students to count the number of objects and match the correct set of dots from one of the rectangles to the actual numeral. Students color in the matching dot pattern. Some students may quickly see the rows of 10, count the two groups of 10 and count on for the next four numbers. Tell students to cross out the dots as they count them for extra support.
Step 6: Wrap Up (5 min)
Review lesson objectives, key vocabulary words, place value, and linking cubes.
