# 2nd Grade Resources

## Add and Subtract 1 and 10

This is meant to develop understanding of addition and subtraction of 1 and 10. You are given a starting number and and ending number (the relationship between having been determined by the adjustable "Difficulty"). Your job is to get to the ending number by adding or subtracting one(s) or ten(s). Choose a representation to help your thinking and try to find the most efficient pathway. ## Addition Strikes

What are the missing digits of this equation? Think strategically about the possibilities, then click the buttons to find out. Play this game slowly with lots of conversations about what you know/don't know. See this Marilyn Burns blog post for more information and instructional ideas. ## Advanced Number Path

This is a hundreds chart, but with a twist. Every number in the hundreds chart has been multiplied by a random number [1,10]. Can you figure out the pattern? (See also Number Path, which explores the same idea on a normal hundreds chart.) ## Balance (The Farmer's Stone)

There's a sack on a scale. How much does it weigh? Use the weights to find out and explore flexible approaches to equality. ## Bar Graphs

Similar to Cats, Cows, Dogs, Horses, but with the data provided as bars (either horizontal or vertical) instead of pictures. You are asked a variety of questions. Feedback provided. ## Broken Clock (2nd 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 has minutes on multiples of 5; the third grade version can be any time. ## 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. ## Cats, Cows, Dogs, Horses

A randomly generated graph. Interpret the graph to answer the following questions (feedback provided):

- How many total animals?

- Are there more ____ or ____?

- How many more ____ than ____? ## 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? ## Close to 1000

Arrange the digits 1-9 into three 3-digit numbers. Try to get the sum as close to 1000 as possible. ## Commuting Counters

Enter two addends, then click next. The addends will show up as counters. Keep clicking next to see the commutative property in action. ## Five by Five

A 2-player, GeoGebra version of Sara VanDerWerf's game. You will place (up to) 25 numbers in the grid. You score by placing (by clicking) matching numbers in adjacent squares. Decide whether you want to play a timed or untimed game, and whether you'd like the scores to be calculated by sums or products. See Sara's blog post for more information. ## Fraction Bars and Fraction Wedges

Two similar tools for recognizing and comparing fractions.  ## How Many?

A random number of objects (between 0 and the upper limit you specify) flashes on the screen. Estimate how many you saw. Then display the picture again, reconsider your guess, and finally see the answer. Designed to develop solid connection between a number and how "big" it actually is. ## How Many? (with grouping)

An updated version of "How Many?" with a new feature: once you see the squares, you can arrange them into groups. Use this to connect estimation and quantity to skip counting. Or use it to have a conversation about multiplication or division. ## Interactive Number Grid

This grid goes to 120. Click on the numbers to toggle the colors. Click on an arrow to turn the entire row or column red. Explore 1 or 10 more/less, patterns in skip counting or beyond. ## Make a Dollar

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

Enter any number of hundreds, tens, and ones to see that number drawn in any of three ways. One way of using this is to help students see the difference between a digit and its value. For example, a student might say the number 63 has 60 tens and 3 ones. If you enter that in this applet, you can see a number represented as...

• 60 tens and 3 ones ("How I typed it")
• 6 hundreds and 3 ones ("Standard place value")
• 603 ones ("All ones") ## Move the Number

This activity is meant to develop flexible, creative thinking about numbers and operations. Your goal is to move a from a starting number to a target number, but there are many ways to do this! Adjust the sliders to control the bounds of the numbers involved. ## Number Balance

Explore ideas around equality, decomposition, missing addends, and more! Up the ante by finding the mystery number. ## Part-Part-Whole Estimation

Adjust the slider to control the size of the numbers. One of the pieces (a part or the whole) is randomly provided. Use estimation to fill in the rest. Feedback provided. ## Part-Whole Rectangles

Designed to develop ability to estimate reasonable answers in subtraction situations. Specify your own subtraction problem (or generate a random one), then represent the relative size of the subtrahend by shading a rectangle representing the minuend. Feedback on accuracy of shading is provided. (Not included but recommended: finish by estimate the size of the difference before actually doing the subtraction.) ## Partial Number Line

Meant to help develop the idea of possible rounding outcomes by exploring the numbers on an interval of 10, 100, or 1000. Name numbers on an interval (and predict their location!) or drag a randomly generated number to the correct spot (with feedback on the placement provided). ## Piggy Bank

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

Enter a whole number (under 1 million) and it will be shown as a bar partitioned along base-10 values. Use this for a visual demonstration of, for example, why 543 > 345, beyond "because 5 is bigger than 3". ## Placing Whole Numbers on the Number Line

Drag whole numbers to the correct locations on a (mostly) blank number line. Feedback provided. Adjust the upper limit for the size of the number and how many are placed on the line. ## Showing Numbers with Place Value

Enter a number (up to 1000), then regroup it into ones, tens, and hundreds. See also "Making Tens." Designed to allow students to see lots of equivalent representations of numbers. ## Splitting 100

This is meant to help students see the relationship between coins and numbers. Begin the discussion by asking them what they notice as you cycle through the different versions of splitting up the 100 (controlled by the "Switcher" slider). The work to make connections between the bundles/groups and various coins. See below for a potential prompt.  ## Subtraction on Number Line

Designed to develop a specific strategy when faced with a regrouping problem in subtraction. Specify a subtraction problem, then see that represented on the number line as the distance between the two numbers. Since that is a fixed distance, explore how it can be found by adjusting the minuend and subtrahend to generate equivalent subtraction problems, some which would not require regrouping. ## Sums to 100

This Open Middle task is designed to get students thinking flexibly about using place value in addition. Arrange the digits to create three 2-digit numbers. Use trial and error to get your sum as close to 100 as possible. Can you get it to be exactly 100? ## 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? ## Vertical Partitions - Square vs. Circle

Can we partition a circle the same way we partition a square? This applet allows you to compare the resulting areas of vertical partitions in each shape. Adjust the slider to change the denominator then click the button to see the transformation. ## Volume Guesser

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

Use this activity to develop definitions of simple polygons by noticing patterns. Build math language from informal to formal. ## What's the Number?

A random number (upper limit is adjustable) is generated and placed on a blank number line. Your job is to guess where it landed. Click "more info" to zoom in and refine your guess. ## Year Zoom

Start by looking at a year, then gradually zoom in through the month/day/hour/minute. 