Unit 3 Contents

Factors and Primes

1. Determine which of the following are prime numbers. If a number is prime, tell how you know. If it is not prime, write it as the product of prime factors.
1. 6
2. 17
3. 12
4. 39
2. Use factor trees to factor each of the following numbers into primes. Write multiplication sentences to show your answers.
1. 20
2. 28
3. 60
4. 48
5. 54
6. 72
7. 100
8. 42
3. Find the prime factorizations of each of the following numbers. Write your answers using exponents.
1. 50
2. 66
3. 96
4. 300

More Number Riddles

Show or tell how you solve each of these number riddles. Use words such as multiple, square number, factor, and prime in your explanation.

4. I am a multiple of 2. I am not a multiple of 3. I am greater than 10 but less than 20. I am not a square number. What number am I?
5. I am between 6 and 35. I am one more than a square number. Five is one of my factors. What number am I?
6. I am the smallest square number that has the factors 2 and 3. What number am I?
7. Write your own number riddle, similar to the ones in Questions 4–6. Use some of the following words: multiple, factor, prime number, and square number.