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Multiples
Use the rectangles the class made to answer the following questions:
- Which numbers have rectangles with 2 rows? List them from smallest to largest.
- Which numbers have rectangles with 3 rows? List them from smallest to largest.
A number is a multiple of 2 if it equals 2 times another whole number. If you can make a rectangle with 2 rows for a number, then it is a multiple of 2.
Numbers that are multiples of two (2, 4, 6, 8, etc.) are called even numbers. Numbers that are not multiples of 2 (1, 3, 5, 7, etc.) are called odd numbers.
When you skip count, you say the multiples of a number. For example, skip counting by 3 gives the multiples of 3. The multiples of 3 are 3, 6, 9, 12, and so on. They are all the numbers that have rectangles with 3 rows.
- Which numbers on the chart are multiples of 4 (have a rectangle with 4 rows)? List them from smallest to largest.
- Which numbers on the chart are multiples of 5? List them from smallest to largest.
Prime Numbers
- How many different rectangles can you make with 5 tiles?
- How many with 7 tiles?
Numbers that are larger than one and have only one rectangle have a special name. They are called prime numbers. For example, 5 and 7 are prime numbers.
- List the prime numbers between 1 and 25.
- Are all odd numbers prime? Explain.