Big Ideas:
Numbers can be added more efficiently by combining groups of 5 and 10.
When we add a 10 to a 2-digit number, the tens place increases by one ten and the ones place stays the same.
In second grade, students see ten ones as also one ten or one group of ten. Solving problems involving 'friendly' numbers or 'landmark' numbers helps students solve problems within 100 efficiently. Students will use what they know about combinations of ten to help them solve problems involving tens and multiples of ten. When solving problems on the number line, students will keep one number whole and add or subtract the other number in parts. This lesson sets the foundation for students to see a number as tens and ones and be able to efficiently add or subtract fives and tens to/from any two-digit number within 100.
Vocabulary:
number line, jumping, incrementing, tens, add, total
Special Materials:
manipulatives that be can be grouped into tens and ones (optional)
class 100 chart (optional)
individual 100 chart (optional)
number line to 100 (optional)
Lesson plan