Lesson 7

Workshop: Place Value Concepts

Est. Class Sessions: 2-3

Daily Practice and Problems

Teacher Notes
X
  1. Mack did not add 50 + 9, but instead dropped the plus sign and put the digits together.
  2. 59

X. Mack's Mistake

Here is how Mack solved 38 + 21. He got an answer of 509. Can you find his mistake?

38 = 30 + 8
21 = 20 + 1
50 + 9 = 509
  1. What did Mack do wrong?
  2. What is the correct answer to Mack's problem?