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: inputs 7 and 9 share the output 3
   • No: the outputs do not change by the same amount
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?

   • No: input 6 has two outputs, 14 and 20
   • Yes: inputs 1, 3, 6 and 8 each have an output
   • No: input 3 has two outputs, 9 and 11
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 -3 sends arrows to 4 and 2
   • No: input 0 sends arrows to 2 and 5
5. 4.

   Bo copies a mapping from the board, using a very long ruler for the arrows. Is it a function, and why?

   • Yes: inputs -2, -1, 1, 2 and 4 each send one arrow
   • Yes: no two arrows land on the same output
   • No: inputs -2 and 2 both send an arrow to 3
6. 5.

   (5, -1), (-3, 4), (0, 6), (5, 2), (2, 4). Kira writes clue points for a grid game, and two clues fight over input 5. Is it a function, and why?

   • No: input 5 has two outputs, -1 and 2
   • No: inputs -3 and 2 share the output 4
   • Yes: inputs -3, 0, 2 and 5 each have an output
7. 6.

   Tala times a 200 m race: lane 2 runs 38 seconds, lane 4 runs 41 and lane 5 runs 38. Input: lane. Output: time. Is it a function, and why?

   • Yes: each lane has just one time
   • No: lanes 2 and 5 share a time
   • Yes: no time appears twice
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?

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

9. Use the table

   input: x	output: y
   2	-3
   5	4
   -1	0
   3	4

10. 8.

    Ari tests a rule card in math club. What is the range (all the outputs)? List each value once.

    -3, 0, 4
11. 9.

    Kira's table got scribbled on by a very excited pen. This table is not a function. Which input has two different outputs?

    7
12. 10.

    Pia rides a scooter on a 3-mile path. The time it takes depends on the speed. Which amount is the input (independent variable)?

    • The input is the 3-mile path
    • The input is the time it takes
    • The input is the speed