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. 1.

   (4, -2), (-3, 5), (4, -2), (1, 0), (-3, 6). Two inputs repeat in Esme's list of points. One repeat is harmless; one is not. Is it a function, and why?

   • No: input -3 has two outputs, 5 and 6
   • Yes: inputs -3, 1 and 4 each have an output
   • No: input 4 appears in two pairs
2. 2.

   Jun plots six points in all four quadrants for a star map. Is it a function, and why?

   • No: the points are in all four quadrants of the grid
   • No: (2, -4) and (2, 1) are on one up-and-down line
   • Yes: no two points are at the same height
3. 3.

   Kira plots a zigzag path for a toy car race on a grid. Is it a function, and why?

   • Yes: inputs -5, -3, 0, 1, 3 and 5 each have one point
   • No: (-3, -1) and (1, -1) are at the same height
   • No: the points are not on one straight line
4. 4.

   The pond was 14°C at 9 a.m., 19°C at noon and 14°C at 6 p.m. Milo makes temperature the input and time the output. Is it a function, and why?

   • No: the times are not evenly spaced, so the rule fails
   • No: 14°C goes with two times, 9 a.m. and 6 p.m.
   • Yes: every temperature has a time
5. 5.

   On a winter day it was -2°C at 6 a.m., 5°C at noon and -2°C at 9 p.m. Noah makes time the input and temperature the output. Is it a function, and why?

   • No: the temperature goes up, then comes back down
   • Yes: each time has just one temperature
   • No: 6 a.m. and 9 p.m. share -2°C
6. 6.

   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?

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

   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. Read this first

   Use the table

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

9. 8.

   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. 9.

    (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. 10.

    Ari plots points for a robot's path, and the robot got confused. This graph is not a function. Which input has two different outputs?

    -2