SWBAT will practice addition and subtraction with regrouping by independently searching a database for information about the last volcanic eruptions in Oregon, or Washington, Idaho and Wyoming. They will use this information to calculate elapsed time and record their data on a table and graph.

The advent of the internet has given us phenomenal access to real-world data that we can use to make practicing basic operations more relevant and interesting for students.

10 minutes

This is the third, and last day, of direct instruction in the review of addition and subtraction strategies. Students who demonstrated through their work, mini-lesson performance (monitored with a checklist as I looked at their whiteboards) and a few 1-1 mini-meetings that they are successful with this may skip this mini-lesson and get right to work on their volcano data search.

Today I review again:

- standard algorithm for addition, expanded form and partial sums for addition, and equal and opposite change
- standard algorithm for subtraction, expanded form for subtraction and equal change

Today I do only one problem in each area, unless a clear need is demonstrated for more. I monitor student work and participation and will again keep struggling students with me, where we might just review the plain skill without the overlapping volcano content. It is late enough in the year that if they are not mastering these skills it's time for intensive intervention.

45 minutes

At this point, students are really becoming fluent with the specific technology and math skills required for this lesson. I walk around the room to assist students who still need a bit more direct instruction on both how to manipulate the Smithsonian *Global Volcanism* database and the steps for setting up their number line to calculate elapsed time in hundreds or thousands of years.

I run through a few examples with "just the numbers" prior to using actual dates from the database. Calculating elapsed time in centuries AD often involves more steps but it's not as conceptually difficult as calculating elapsed time in centuries with a BC/BCE starting point.

As students work through the Volcanoes of Oregon or Volcanoes of Washington, Idaho, and Wyoming student pages, I carry a Volcanoes of Oregon KEY and a Volcanoes of WA, ID, WY KEY because it facilitates my ability to pinpoint specific student errors and ask the right types of questions to guide them back to the correct procedure.

5 minutes

**I ask students to explain/teach their preferred strategy to a partner. ** They need to lead their partner through each step using specific language. This is why I like students as teachers.

Some comparison examples:

Student "teacher": The first step is to break up the number.

Teacher: First we will take the number 459 and separate the hundreds, tens and ones as we write it as 400 + 50 + 9 =

Student: "Then do this..."

Teacher: Line up the numbers so that you are adding ones to ones, tens to tens and hundreds to hundreds.

**An alternative wrap up conversation is to have students explain, verbally or in writing, which one is their favorite strategy and why.**

"I prefer expanded form because..."

"I like to use the standard algorithm because..."

"Something I find helpful about expanded form is..."

"A part of the standard algorithm that helps me understand addition is..."