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

Answer Key - Grade 8 Math Worksheet - Challenge Me

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

1. Read this first

   Use the table

   input: x	output: y
   -2	5
   1/2	3
   4	-1
   -2	5
   3	3
   6	0

2. 1.

   Ren copies a rule table from the board and writes one row twice. Is it a function, and why?

   • Yes: inputs -2, 1/2, 3, 4 and 6 each have one output
   • No: input -2 appears in two rows
   • No: the outputs do not change by the same amount each time
3. 2.

   Tala checks a table on the whiteboard before the bell. Is it a function, and why?

   • No: input -1 has two outputs, 6 and 7
   • Yes: inputs -1, 0, 2.5, 3 and 5 each have an output
   • No: inputs 2.5 and 0 share the output 4
4. 3.

   (-7, 3), (2, -4), (5, 3), (2, -4), (-1, 0), (8, 6). Ari collects points from three classmates, and two of them sent the same one. Is it a function, and why?

   • Yes: inputs -7, -1, 2, 5 and 8 each have one output
   • No: inputs -7 and 5 share the output 3
   • No: input 2 appears in two pairs
5. 4.

   (3, 1/2), (-2, 4), (3, 2), (6, 4), (0, -3). Bo writes points for a grid design of a kite. Is it a function, and why?

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

   Pia scans library books: barcodes 104 and 117 are two copies of Comet Kids, and 125 is Sea Maps. Input: barcode. Output: title. Is it a function, and why?

   • Yes: no title appears twice
   • No: barcodes 104 and 117 share a title
   • Yes: each barcode has just one title
7. 6.

   Ren plots five stops on a hiking map grid. What is the domain (all the inputs)? List each value once.

   -4, -1, 0, 3, 5

8. Use the table

   input: x	output: y
   1/2	3
   2	-1
   4	3
   -3	1/4
   6	5

9. 7.

   Tala fills in a rule table with fractions. What is the range (all the outputs)? List each value once.

   -1, 1/4, 3, 5
10. 8.

    (2, 7), (-6, 0), (2, 7), (1/2, 4), (9, -5). Zee lists points, and one pair got written twice. What is the domain (all the inputs)? List each value once.

    -6, 1/2, 2, 9
11. 9.

    Bo plots where five frogs sit on a pond grid. This graph is not a function. Which input has two different outputs?

    4
12. 10.

    Jun's pairs make a function: (1, 4), (3, 6), (5, 4), (6, 9). Which new pair can join and keep it a function?

    • (3, 8)
    • (5, 1)
    • (2, 6)