Learning Activities: Using a balance scale to demonstrate solving for x

I thought the balance scale would be a great way to demonstrate how simple equations work, and what it means to solve for an unknown. I needed something to hide the unknown quantity under, and an empty plastic Easter Egg met the requirement nicely. I placed the empty egg half on one side of the balance and calibrated the scale (there are sliding weights on the top bar to do this with) so it balanced in the middle. Then I hid 3 gram cubes under the egg, added 5 more to that side and 8 to the other—and showed the children that the two sides of the scale balanced out.

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I asked what that meant—at first they thought the egg shell was adding the extra weight, but I explained that I had adjusted the scale to balance with the egg shell (I should have showed them this before I started). Then I told them there were cubes under the shell and asked them to figure out how many there were. Honeybee figured out that there must be 3, and we lifted the shell to check. Sure enough ,there were three cubes hiding underneath, making 8 on each side—which was why the scale balanced. I then showed them how to write the equation on paper, using an x for the unknown.

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6 Responses to Learning Activities: Using a balance scale to demonstrate solving for x

  1. maryanne says:

    I really love this idea! What a concrete way to introduce algebra =)

  2. Love this activity!! Using an Easter Egg was sheer brilliance. What kid wouldn’t want to find out what’s inside?

    Thank you for your kind comment about my Roman Blind. Fortunately the sewing is limited to straight(ish) lines – the difficult part was figuring out where those lines should go in the first place.

    • thegardener says:

      I don’t know why sewing intimidates me so much–maybe just lack of experience.
      I love finding new ways to make math hands-on and concrete. If figure when my kids get around to the “manipulating abstract symbols” phase of math it will make that much more sense to them.

  3. Karene says:

    I think I am going to be drawing from this blog during the summer…I’ve been thinking it would be good to have some daily lessons to keep Cole’s mind active while he’s not in school. I love your ideas. You are so good at this stuff!

  4. Pingback: Learning Activity: Using a Balance Scale to Demonstrate Solving for X, part 2 | Growing Wisely

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