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Wrecking Ball

Make your own pendulum, then get set to wreck with this simple addition and subtraction game!

Ages: 4+
Players: 2+
Time: 20+ Minutes
Type: physical activities
Location: around the house
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Ages: 4+
Players: 2+
Time: 20+ Minutes
Type: physical activities
Location: around the house

Instructions

Before you play, you'll need to make a pendulum (your "wrecking ball"). Attach one end of a string somewhere at least a few feet off the ground. We attached ours to a dining table using tape.

String taped to the side of a table
One option for attaching your wrecking ball.

Some other options: tie one end to a branch, or attach one end to the top of a door frame. Just make sure that your string is fairly secure, and that there's room at the bottom for your pendulum to swing around without hitting (or breaking!) anything.

At the bottom of the string, attach a weight. We used a spoon and some tape. Measuring spoons or small measuring cups work well because they often have a little hole you can tie the string through.

A measuring spoon tied to string

Attach the weight so that, when it's hanging still, it's just a little bit off the ground.

Now set up 3 blocks or other items labeled 1, 3, and 9. (Don't choose other numbers. These numbers are special because we can combine them in different ways with addition and subtraction to get every number we'll need for the game. See Learning Notes below for more on this.) We used dominoes, but blocks, paper cups, or anything knock-downable will work. Set these up so that they can be hit by the pendulum. The farther apart they are from each other, the harder the game.

The spoon pendulum set up next to three dominoes

Next, make a score card for each player by writing the numbers 1-13 down the side of a piece of paper. (Or, for a shorter, non-competitive game, make one score card to share. See the Collaborative Play variation below.)

Piece of paper with numbers one through thirteen written down the side

Now it's time to wreck! Take turns swinging the pendulum to knock down the numbers. Swing up to three times on your turn. You can knock down one block per swing. (Or, for an easier variation, allow multiple blocks to be knocked down on a single swing. See Variations below for more ideas!)

The spoon pendulum knocking over the three domino
Got the 3!

Use addition or subtraction (or both!) to combine the numbers you hit. Write this on your score card. Then, cross off the resulting number. For example, if you hit 3 and 9, you could write 9 + 3 = 12 and cross off the 12, or you could write 9 - 3 = 6 and cross off the 6.

The equation 1 + 9 = 10 on a score card

What numbers could you cross off your score card if you hit the 1, 3, and 9? You could write 9 + 1 - 3 = 7, for example, but there are other possibilities. Figuring out how to cross off each number on your score card is part of the fun!

When you knock down only one number, it's still best to record this with an equation. If you knock down the 3, write 3 = 3 on your score card before you cross off the 3. (See Equations below for why equations like this are worth writing down.)

The first player to cross off all their numbers, 1 to 13, wins!

Equations written on a score card with all numbers crossed off the list

Don't forget: it's Beast Academy Playground, not Beast Academy Study Hall. Change the rules, be silly, make mistakes, and try again. The Variations and Learning Notes are here for you if you want to dive deeper, but not all of them apply to learners of every age. The most important thing is to have fun.

Variations d

Collaborative Play:

Make just one score card. Players still take turns, but work together to cross off all the numbers. This version of the game is also shorter, which can be helpful for younger kids.

Change the Rules:

Be flexible so the game works for you and your math beast. Here are some ideas:

  • If the numbers are too hard to hit, move them a little closer to the pendulum or a little closer to each other.
  • Let each player have up to 4 swings on a turn.
  • If the wrecking ball hits more than one number on a swing, count both.
  • Let players choose to use only some of the numbers they hit on a turn. So if a player hits 3 and 1, but already has 3 + 1 = 4 and 3 - 1 = 2, they could use just the 3 or just the 1.

Bowling:

Not up for making a pendulum? (You're missing out!) Set up your blocks (or dominoes or whatever you're using) at the end of a hallway and use a tennis ball to bowl them down. Find the right distance so knocking down the numbers isn't too hard or too easy.

Trashketball:

Set out three trashcans or buckets and label them 1, 3, and 9. Throw 3 paper balls on your turn. (And see our game Trashketball for more ideas.)

Addition Only:

For a simpler, shorter game, label your blocks with the numbers 1, 2, and 4 (instead of 1, 3, and 9), and write the numbers 1 to 7 on your score card (instead of 1 to 13). Play as you would for regular Wrecking Ball to knock down the numbers, but when you put them on your score card, use only addition (not subtraction).

Classroom Tips d

Play Wrecking Ball (or the Trashketball variation) to practice simple addition and subtraction under 20, or as a follow-up to a unit on exponents (see Learning Notes).

Discussion Questions

  • What numbers are the easiest to make? What numbers are harder to make?
  • Are there any numbers that can be made in more than one way?
  • What pattern do you notice in the numbers 1, 3, 9. What is the next number in the pattern? (see Learning Notes)

Alignment with Beast Academy Curriculum

  • Level 3: Chapter 3: Exponents (See Learning Notes)
  • More alignment with Beast Academy Level 1 soon!

See Variations and Learning Notes for more ideas on how to adapt this activity and incorporate it into your classroom.

Learning Notes d

Addition & Subtraction Strategies:

Look for ways to help your child with addition and subtraction. When adding 9, 3, and 1, for example, it can help to add the 9 and the 1 first to get 10, then add 3 more to get 13. When first learning addition and subtraction, it's fine to count on fingers. When adding, see if your child can start at the higher number, and count up from there. So in adding 9+3, they would say "10, 11, 12" holding up a finger each time until they have 3 fingers held up.

Equations:

Because kids so often see math problems in the form 2 + 2 = __, they can mistakenly think that an equals sign means, essentially, "what's the answer?" In fact, an equals sign is a way of showing that two amounts are the same! The amount on the left of the equals sign is the same as the amount on the right, like a balance scale. The equation 2 + 2 = 4 tells us that two groups of 2 is the same amount as one group of 4. An equation like 1=1 may seem silly or meaningless if you think an equals sign is asking you to give the answer. In fact, the equals sign is showing that both sides are the same. In the context of Wrecking Ball, an equation like 1 = 1 tells us, "I just need to knock down a 1 to get a total of 1." No addition or subtraction needed!

Powers of Three:

Though young math beasts won't recognize the numbers 1, 3, and 9 as anything special (and that's fine), they are in fact what mathematicians (and middle and high school students) recognize as powers of 3. (3 to the zeroth power equals 1, 3 to the first power equals 3, and 3 to the second power equals 9.)

Wrecking Ball takes advantage of the fact that these numbers can be added or subtracted to make every number from 1 to 13.

Equations using one, three, and nine to make all numbers from one to thirteen

The next power of 3 is 3 to the third power. This means we multiply 3 times itself 3 times, 3 × 3 × 3 = 27. Can your math beast use the numbers 1, 3, 9, and 27 to make every number from 1 to 40?

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Materials
  • string
  • something to tie on (we used a spoon)
  • 3 items to knock down (we used dominoes)
  • paper
  • pencil
Learning Goals
  • addition
  • subtraction
  • writing numbers
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Image of Ms. Q

Ready to level up?

Keep problem solving with Beast Academy’s full math curriculum for students ages 6–13. Check out our captivating comic book series and immersive online platform.

LEARN MORE

Bring problem-solving to your classroom

Keep your entire class engaged with a full book and online math curriculum, for students ages 6–13. 98% of teachers say they’re satisfied with Beast Academy.

LEARN MORE
Image of a BA book