Marbles serve as counters to help students practice basic operations, including addition, subtraction, multiplication and division. To practice addition, students start with two groups of marbles. They count the number of marbles in each group and then combine them to figure out the total. Subtraction practice starts with a large group and asks students to move a certain number of the marbles into a separate group to see how many are left. For multiplication practice, students create groups with equal numbers of marbles. They determine the total number in all of the groups. For division, students start with one large pile of marbles and divide them into equal groups. Have the students write down the corresponding math problems and answers as they work with the marbles.
Marbles in different colors provide the materials for a classroom probability project. You need several marbles in different colors. Place several marbles of each color in a jar or bag. For example, you might use three red marbles, two green marbles, seven orange marbles, five blue marbles and one yellow marble for a total of 18 marbles. The kids calculate the probability of how often each color will be drawn by placing the number of marbles in that color over the total in a fraction. For the red marbles, that would be 3 over 18, which is reduced to 1 over 6. Have the children test the calculations by randomly drawing out a marble. Have the children document which color they draw each time.
Marbles also work well as manipulatives to solve word problems. Write several word problems involving marbles. An example is, "Shannon has five green marbles and seven blue marbles. Tom has nine green marbles and three blue marbles. How many green marbles do they have in total?" Adjust the difficulty and the operations used based on the grade level and the topics you're studying in math. The children can use actual marbles to visualize the problem and help solve it.
A jar full of marbles helps children improve their estimation skills. Place 10 marbles next to the jar so the children get a sense of what that amount looks like. They use that knowledge to estimate how many marbles are in the jar. For another challenge, fill jars of different sizes and shapes with marbles. Have the children make estimates and rank the jars from the least amount to the greatest. Count the marbles as a class to see if they were correct.