Math Lesson Plan: One Hundred Things

I do this lesson at the beginning of math class for about a week or two before the 100th day of class (so we do it at least 10 times), when we count out 100 popcorn kernels and estimate how much volume or space they will take up once they’re popped.


  1. Learning to estimate the volume of 100 things
  2. Learning that the containers for measuring each set has to be the same size
  3. Learning that the objects need to be the same size for accuracy


  1. At least ten containers to put 100 things in, transparent is best, so students can see the 100 things.  (I’ve re-used plastic milk bags (some items take 2-3 bags), washed and dried and cut to the same length, but you could use something you have a lot of, like 4L milk jugs, glass spaghetti sauce jars or Ziplock bags.) JUST MAKE SURE THAT WHATEVER YOU USE, THEY ARE THE IDENTICAL SIZE.
  2. 100 items (unit cubes, snap cubes, paper clips, marbles, new crayons, new pencils, pennies, push pins, popsicle sticks, bread bag plastic closures (plastic squares), toothpicks, math counter chips or bingo chips, dried beans or peas)
  3. marker to mark the estimated fill level and student’s name on container
  4. push pins to attach bags to bulletin board, or a shelf to keep filled jugs/jars/containers on


  1. Give 10 students a handful (about 10) of items to count out a group of 10 for you.  Each time you do this lesson, get 10 different students to help count out the groups of 10 for you.
  2. Tell students that we are going to be estimating how much volume or space this item will take up.  Put 10 items in the container.  Ask student of the day to estimate how much space or volume 100 of the items will take up.  They can even count 10, 20, 30……90, 100 (and gauging higher and higher) to make a better estimate.
  3. Dump out your 10 items.  Draw a straight black marker line on the outside of the container and print the student’s name above the line (if you wish) to show his estimation.
  4. Gather the groups of 10 items from the ten students, having the class count by 10’s as you fill the container, 10…20….30………80, 90, 100.
  5. Talk about how close the student came in their estimation.  If you have a flat bag, talk about how the bag has expanded from front to back and how this might have changed the position of the estimation line  (items went wider with the bag, rather than up higher in the bag).  Talk about having the same size container for measuring the 100 items, every time you measure a different item.  What would happen if the container were taller? (fill line would be higher)  What would happen if the container were wider?  (fill line would be lower)
  6. Talk about the size of the item you used to count to 100.  What might have happened to the fill line if the item had been smaller?  (it would have been lower) Why?  (smaller doesn’t take up very much room) What might have happened to the fill line if the item had been larger? (it would have been higher) Why?  (bigger things take up more space)
  7. Talk about how fast it is to count to 100 when the groups are already counted into smaller groups of 10.  Regrouping a large number of items into smaller groups is a great way to count larger numbers.   When have we regrouped a large group of something into smaller groups to make it easier for us to count them?  (Sometimes we circle groups of 10 on a worksheet so that we can count a large number of items, or we put them in little piles of 10, or we attach groups of 10 popsicle sticks with an elastic band, or we make tally marks to keep track of oral counting.) (See lessons “Popsicle Stick Regrouping Fun“, “Hugs and Tallies“,  counting by 2’s, 5’s, 10’s, see lesson “Calendar Counting“, “Counting by 5’s Handprints“, “Bingo Dabbing by 5’s“.)

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