Is it a function? Inputs, outputs, domain and range

Answer Key - Grade 8 Math Worksheet

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

1. Read this first

   Use the table

   input: hours after noon	output: temperature in °C
   7	3
   2	8
   5	6
   9	3
   4	10

2. 1.

   On a chilly day, Ren reads the thermometer at different hours after noon. Is it a function, and why?

   • Yes: inputs 2, 4, 5, 7 and 9 each have one output
   • No: the outputs do not change by the same amount
   • No: inputs 7 and 9 share the output 3
3. 2.

   At an ice cream cart, Tala writes the people in line and the minutes waited, over two sunny days. Is it a function, and why?

   • Yes: inputs 1, 3, 6 and 8 each have an output
   • No: input 3 has two outputs, 9 and 11
   • No: input 6 has two outputs, 14 and 20
4. 3.

   Ari draws a mapping for math club, and the arrows look like spaghetti. Is it a function, and why?

   • Yes: inputs -3, 0 and 2 each send an arrow
   • No: input 0 sends arrows to 2 and 5
   • No: input -3 sends arrows to 4 and 2
5. 4.

   Esme checks a classmate's mapping before it goes on the wall. Is it a function, and why?

   • No: input 4 sends arrows to 2 and 9
   • Yes: inputs 1, 4, 6 and 8 each send an arrow
   • No: inputs 1 and 6 both send an arrow to 7
6. 5.

   Noah plots points from a math club rule card. The rule card has a juice stain on it, but the points are clear. Is it a function, and why?

   • No: the points are not on one straight line
   • Yes: inputs -3, -1, 0, 2 and 4 each have one point
   • No: (-1, -1) and (2, -1) are at the same height
7. 6.

   In a video game level, Pia plots where four stars sit on the grid. Is it a function, and why?

   • Yes: inputs -4, -2, 1 and 3 each have one point
   • No: the points are not on one straight line
   • Yes: the points are evenly spaced along the grid
8. 7.

   In Zee's bike rack, bike 3 has 7 gears, bike 8 has 21 and bike 12 has 7. Input: bike number. Output: gears. Is it a function, and why?

   • Yes: no gear count appears twice
   • Yes: each bike has just one gear count
   • No: bikes 3 and 12 share a gear count
9. 8.

   Esme plots the stars in a game level. What is the range (all the outputs)? List each value once.

   -2, 1, 5
10. 9.

    Milo prints a 12-page comic. The more pages, the longer the printing takes. Which amount is the input (independent variable)?

    • The input is the printing time
    • The input is the printer
    • The input is the number of pages
11. 10.

    Noah bakes cookies, 15 on each tray. The number of cookies depends on the number of trays. Which amount is the input (independent variable)?

    • The input is the oven
    • The input is the number of cookies
    • The input is the number of trays