Every number bigger than 1 is either a prime or a stack of primes multiplied together. Breaking a number down into its primes is like taking apart a machine to see what it's made of.
Not started yet.
By the end of this lesson your student should be able to tell a prime from a composite number, and write the prime factorization of a composite number with a factor tree or by dividing by the least prime, using exponents for repeats.
đ¨ Calling 1 a prime. A prime needs exactly two factors, and 1 only has one, so 1 is neither prime nor composite.
Stopping a factor tree too early, with a composite number like 4 or 10 still sitting at the end of a branch.
Thinking different trees give different answers. They look different and always end in the same primes.
Have the student multiply the primes back together at the end of every problem. If the product doesn't match the number he started with, a prime went missing.
Read-aloud is not available in this browser. Try Chrome or Safari.
Before You Start
The words this lesson uses. Tap a card to see what it means, then come back to them whenever a question uses one.
Part One
Questions about the story you just read. Pick your answer straight off, or press Find it in the story if you would rather hunt for the sentence first.
Part Two
The word cards are at the top of this page. Look back at them as often as you need, then answer.