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?

   • No: inputs 7 and 9 share the output 3
   • Yes: inputs 2, 4, 5, 7 and 9 each have one output
   • 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?

   • 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.

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

   (-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?

   • No: input 1 appears in two pairs
   • Yes: inputs -4, -2, 1 and 3 each have one output
   • Yes: no input appears twice, so the list has no repeats
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: inputs -3 and 2 share the output 4
   • No: input 5 has two outputs, -1 and 2
   • Yes: inputs -3, 0, 2 and 5 each have an output
7. 6.

   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
   • No: (-1, -1) and (2, -1) are at the same height
   • Yes: inputs -3, -1, 0, 2 and 4 each have one point
8. 7.

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

   -2, 1, 5

9. Use the table

   input: x	output: y
   4	1
   7	9
   2	6
   7	3
   5	6

10. 8.

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

    7
11. 9.

    Two buses' counts got mixed into one table of (minutes after 3:00, kids on board). Luz spots the problem. This table is not a function. Which input has two different outputs?

    12
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