This Fluency Activity is a part of the Lesson 7, Unit 3, Grade 2. Sometimes a line of questioning can be further broken down to scaffold for English language learners or students working below grade level. It is much easier to see the change in the tens place when the value is expressed in unit form. Add the $10 and give wait time. "4 tens 5 dollars plus $10 is? (provide sufficient wait time) 5 tens 5 dollars."