## Area and Perimeter of a Rectangle

See the area and perimeter of any rectangle.

## Broken Clock (3rd grade version)

Estimate the random time shown by only the hour hand. Click a button to slowly put the clock back together and refine your estimate. This version can be any time; the second grade version has minutes that are multiples of 5.

## Cash Register

Set the max price, then click start. A random price is generated for an item. Drag the coins onto the cash register to pay for it. Toggle the "Show total" to see how much you've paid (if needed), then click "Check" to see if you've paid the right amount.

## Clock

A simple tool for exploring how a clock works. How does the minute hand move compared to the hour hand? What do we know about what time it is by looking at the hour hand?

## Connecting Perimeters

Use this for a conversation for the perimeter and/or area of a complex polygon composed of non-overlapping rectangles. Drag the blue points to create a shape, then click one of the two buttons. Drag the sliders to move the sides.

## Elapsed Time

Set a start and end time. The elapsed time is shown by unwrapping the number line from the clock. Several options for what is displayed.

## Elapsed Time on Number Line

This is based on the idea that we could approach elapsed time by comparing the relative size of the interval to the length of a day. The discussion at the end begins with "So how long would that be?" Use these visuals to make predictions, then compare it to the precise answer you get from whatever strategy you use.

## Make a Dollar

Drag coins onto a dollar bill until you've got \$1.00 in pennies, nickels, dimes, and/or quarters.

## Missing Side Lengths (Complex Polygon)

A randomly generated (L-shaped) complex polygon starts as just two sides. Drag the sliders to make the rest. Meant to allow students to see the part/part/whole relationship between opposing sides.

## Perimeter and Area of a Rectangle (Animated)

Drag the point to change the dimensions of the rectangle. Then click the "Go" button to see the perimeter upwrap and the area fly out. Perimeter and area lie along the number line to allow conversations about their value. Works better for small rectangles.

## Piggy Bank

Drag coins or \$1 bills into the piggy bank. Click to show the total amount.

## Separable Clock

A simple tool that allows you to separate the hour and minute hands of an analog clock in order to analyze them independently.

## Two Piggy Banks

Drag coins onto both banks (or Fill Randomly on both)

• Which bank has more? (I like that there'd be lots of ways to answer this)

• What coins would we add to make the banks equal?

Drag some coins onto one piggy bank (or Fill Randomly)

• Students tell you the value. Click to show total.

• Students tell you another way to reach the same total. Drag that onto the other piggy bank. Click show totals for both. Do they match?

## Volume Guesser

Select the units you want to use, then guess the volume of the liquid in the container. Feedback provided.

## What's Happening? Area and Perimeter

This is a set of three dynamic illustrations meant to develop understanding of perimeter and area. "What's happening to the perimeter? What's happening to the area?" See also this student handout.