Using graham crackers, you can help students visualize the concept of multiplying whole numbers by fractions. Give a student a graham cracker, explaining it represents the number 1. Have him break it in half and note how many pieces there are now: 1 divided by 1/2 is 2. Repeat the process with two crackers. What is 2 divided by 1/2? Have him break the two crackers in half to create four pieces: 2 divided by 1/2 is 4. This paves the way to show how to divide fractions without using graham crackers, by inverting the fraction and then multiplying -- 1 divided 1/2 would be 1 x 2/1, which equals 2.
This is a good activity to introduce as the Easter holiday approaches. It will challenge fourth-graders to understand abstract problems using jellybeans. You'll need a bunch of jellybeans and some small baskets or jars. Place a particular number of jellybeans of certain colors in each basket and then present the class with some brainteasers. Use purple, yellow and pink candies. Using clues, students must determine how many of each color jellybean are in each basket. In example one, present these clues: Basket No. 1 has three purple jellybeans and twice as many pink jellybeans as purple ones. There are 12 jellybeans in all. How many of each color are there? The answer is three purples, six pinks and three yellows. In the next example, present these clues: Basket No. 2 has 16 jellybeans. Half of them are pink and a quarter of them are yellow. The answer is there are eight pinks, four yellows and four purples. See if the class can make up their own puzzlers.
You can give this exercise a holiday twist as Christmas and Hanukkah approach. It will sharpen math skills, while teaching students about budgeting and money handling. Cut out a couple dozen items from newspaper ads and fliers, making sure the prices are visible. Have the students prepare a list of a least five people for whom they want to buy presents and assign them a budget; for example, they have just $100 to spend. Mount the items on a poster board. Have students approach it to begin their "shopping." Each student must select one item from the board and then subtract the cost of that item from her budget. Now she knows how much she has left to spend. Repeat the process for two more gifts. After three "shopping excursions," have the students note how much money they have left and whether they need to exchange gifts before continuing. After all five gifts have been "purchased," have the students show their work. Five gifts must have been purchased without going over the budget. You can also do this exercise any time of year using ads from the grocery store.
This is a good exercise to introduce fourth-grade students to some basic geometry concepts. Review the formula for calculating volume: length x width x height = volume. Have the students build rectangle prisms of any size using sugar cubes. They should start small. Have the students record the dimensions of their creations. How many cubes long is it? How many cubes tall? How many wide? Have them substitute these dimensions into the volume formula and note the answer. Have the students check their answers by taking apart their prisms and counting the cubes. As the students get the hang of it, have them build another, bigger model, and try to work the formula again.