


The Wonder Number Lessons
Lesson No. 10: Primes and Composites Knowing the difference between a prime number and a composite number is one of the most important facts a student will ever learn in math. It is a crucial piece of information that is relevant in everything from basic math to calculus. The Wonder Number Board is the best way for students to grasp this abstract concept because it provides visual evidence that reinforces the definitions of these two different types of numbers. A prime number is one that is divisible only by one and itself. Prime numbers on the Wonder Number Board are designated with a circle around the number and lists only 2 factors, 1 and itself. First place a viewer on number 11. The student will discover that 11 is a prime number because it has a circle around it and has only 2 factors, 1 and itself. Try several different configurations using eleven chips on the board to prove that it is not possible to make a rectangular array (see fig 53). This proves that 11 is a prime number. Place a viewer on number 13. The student will discover that 13 is a prime number because it has a circle around it and has only 2 factors, 1 and itself. Try several different configurations using thirteen chips on the board to prove that it is not possible to make a rectangular array (see fig 54). This proves that 13 is a prime number. Place a viewer on number 19. The student will discover that 19 is a prime number because it has a circle around it and has only 2 factors, 1 and itself. Try several different configurations using nineteen chips on the board to prove that it is not possible to make a rectangular array (see fig 55). This proves that 19 is a prime number. A composite number is a number that has more than 2 factors. Composite numbers have all of their factors listed inside each block. First place a viewer on number 6. The student will discover 6 is a composite number because it has more than 2 factors. The factors of 6 are 1, 2, 3, and 6. Next take six chips and make two different rectangular arrays on the board. The possibilities are 2 sets of 3 and 3 sets of 2 (see fig 56). Place a viewer on number 8. The student will discover 8 is a composite number because it has more than 2 factors. The factors of 8 are 1, 2, 4, and 8. Next take eight chips and make two different rectangular arrays on the board. The possibilities are 2 sets of 4 and 4 sets of 2 (see fig 57). Place a viewer on number 15. The student will discover 15 is a composite number because it has more than 2 factors. The factors of 15 are 1, 3, 5 and 15. Next take fifteen chips and make two different rectangular arrays on the board. The possibilities are 3 sets of 5 and 5 sets of 3 (see fig 58). The number 1 is neither prime nor composite. 1 is unique. It has only one factor, 1.

