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.

   Zee measures a sprout on some days and writes day 4 twice. It grew slowly after day 7. Is it a function, and why?

   • Yes: inputs 1, 4, 7 and 10 each have one output
   • No: input 4 appears in two rows
   • No: the outputs do not change by the same amount
4. 3.

   (-4, 2), (1, -3), (3, 5), (1, -3), (-2, 0). Jun copies points from the board and writes one of them twice. Is it a function, and why?

   • Yes: inputs -4, -2, 1 and 3 each have one output
   • No: input 1 appears in two pairs
   • Yes: no input appears twice, so the list has no repeats
5. 4.

   Milo plots the stops for a park clue walk on a grid. Is it a function, and why?

   • Yes: no two points are at the same height
   • No: (1, -2) and (1, 4) are on one up-and-down line
   • No: some points are below the x-axis
6. 5.

   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
7. 6.

   Ren's weather log: Monday 64°F, Tuesday 70°F, Thursday 64°F. Input: temperature. Output: the day. Is it a function, and why?

   • Yes: every temperature has a day
   • No: 64°F goes with two days, Monday and Thursday
   • No: Wednesday is missing, so the log is not complete

8. Use the table

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

9. 7.

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

   -3, 0, 4
10. 8.

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

    -2, 1, 5

11. Use the table

    input: x	output: y
    3	8
    6	5
    1	8
    6	2
    9	4

12. 9.

    Jun checks a classmate's table in math club. This table is not a function. Which input has two different outputs?

    6
13. 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 speed
    • The input is the time it takes