Constructing a piecewise model

Write a separate rule for each part of a situation’s domain.

  • Identify where the rule changes.
  • Use inequalities that include the boundary exactly once.
  • For a charge above a threshold, charge the extra rate only on the amount above that threshold.

Example

A delivery charge

Write a piecewise function to model the cost. Delivery costs $6 for a positive weight up to 3 pounds, then $2 per pound above 3 pounds.

Your turn

5 practice questions
Question 1

A delivery costs $5 for a positive weight up to 2 pounds. Above this, add $3 per pound over 2 pounds. Write .

Check answer
Question 2

A delivery costs $8 for a positive weight up to 4 pounds. Above this, add $2 per pound over 4 pounds. Write .

Check answer
Question 3

A delivery costs $10 for a positive weight up to 5 pounds. Above this, add $4 per pound over 5 pounds. Write .

Check answer
Question 4

A delivery costs $4 for a positive weight up to 1 pounds. Above this, add $2 per pound over 1 pounds. Write .

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Question 5

A delivery costs $12 for a positive weight up to 6 pounds. Above this, add $3 per pound over 6 pounds. Write .

Check answer