Piecewise and step functions: evaluate and graph

Answer Key - Grade 9 Math Worksheet - Building Confidence

Circle the best answer, or write your answer on the line.

1. 1.

   Esme's scooter fare is f(x) = x + 2 when x < 3 and f(x) = 2x when x ≥ 3. Since 5 is at least 3, use 2x. What is f(5)?

   10
2. 2.

   Jun's bike score is f(x) = 3x when x ≤ 2 and f(x) = x + 4 when x > 2. Since 1 is at most 2, use 3x. What is f(1)?

   3
3. 3.

   Kira's price is f(x) = 10 − x when x < 4, f(x) = 2x + 1 when x ≥ 4. Since 7 is at least 4, use 2x + 1. What is f(7)?

   15
4. 4.

   Luz's robot score is f(x) = 5x when x ≤ 1 and f(x) = x + 9 when x > 1. Since 6 is more than 1, use x + 9. What is f(6)?

   15

5. Read this first

   Parking costs (hours)

   Up to 1 hour $3; up to 2 hours $5; up to 3 hours $7; up to 4 hours $9.

6. 5.

   Milo parks a car at a lot. What does 1.5 hours cost?

   $5
7. 6.

   Pia parks a bus at the same lot. What does 3.2 hours cost?

   $9
8. 7.

   Up to 1 oz $0.50; up to 2 oz $0.75; up to 3 oz $1.00; up to 4 oz $1.25. Ren mails a stack of paper that weighs exactly 3 ounces. What does the stamp cost?

   $1
9. 8.

   Tala scores a game with f(x) = 3x when x ≤ 2 and f(x) = x + 4 when x > 2. Which rule do we use for x = 2?

   • 3x, because x ≤ 2 includes 2
   • x + 4, because 2 is where the rule changes
   • Both rules, then add them
10. 9.

    Zee counts coins with f(x) = x + 1 when x < 5 and f(x) = 2x when x ≥ 5. Which rule do we use for x = 5?

    • Both rules, then add them
    • x + 1, because 5 is where the rule changes
    • 2x, because x ≥ 5 includes 5
11. 10.

    Ari drums for a game with f(x) = 2x when x ≤ 3 and f(x) = x + 6 when x > 3. Which rule do we use for x = 3?

    • Both rules, then add them
    • x + 6, because 3 is where the rule changes
    • 2x, because x ≤ 3 includes 3