# Group and Independent Practice: Multiplying and Dividing with Powers of Ten

## Activity #1: Moving digit cards

There was still confusion after the activity described in our last blog. Normal, but corrigible! We had students draw a Place Value Chart on an 11 x 17 piece of paper. Something like this:

We had digit cards already (from last year), but students could make those too. This student hs just laid out the number 41:

We wrote up one problem at a time, and students moved their digits right or left accordingly.

Here’s 21 x 10:

Here’s what’s hard: Don’t talk! Don’t tell them which way to move the cards, and how many spaces. So hard! Trust their thinking skills. They will eventually figure it out, and someone can come up and explain why they got what they did. It takes a long time, but they are connecting the dots, connecting neurons, and building confidence that math is “what they can SEE and talk through.”

You could make up as many or few  problems as your class needs. For example,

21 x 10

21 ÷ 10

4.2 x 100

4.2 ÷ 100

Then move to 2-step problems. Here’s 41 ÷ 20.

Dividing by 20: First divide by 10, giving 4.1. Then divide by 2, but how to divide the 1 in half?  WAIT. Let them talk it out. Think pair share… whatever works to get them thinking and talking.

Trust: someone will see this, and it will spread: One tenth is also 10 hundredths! So add a zero. Now you can divide 10 hundredths in half 🙂

2.4 ÷ 20

2.5 ÷ 20

2.4 x 20

2.4 x 300

## Activity #2: Independent Practice

Here’s the worksheet we used next:

CW 11_27