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Grade 5 Math · Level 1, Place Value & Powers of 10

Factorials & Perfect Squares

How the lesson starts: Factorials & Perfect Squares

1. Puppy photo day

   Welcome to Puppy Park photo day! Coach Benny has 5 puppies to line up for a picture. How many different orders could they stand in? The answer uses a number with an exclamation mark: 5 factorial!

2. Factorials

   Factorial means multiply the number by every whole number below it, down to 1. 3! = 3 × 2 × 1 = 6. 4! = 24. 5! = 120. So 5 puppies can line up 120 ways! And 6! = 6 × 120 = 720.

3. Perfect squares

   Now 36 puppies stand in a square: 6 rows of 6. A perfect square is a whole number times itself. 6 × 6 = 36. It's also the area of a square with side 6. So 36 is 6 squared!