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: the outputs do not change by the same amount
   • Yes: inputs 2, 4, 5, 7 and 9 each have one output
   • No: inputs 7 and 9 share the output 3
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 6 has two outputs, 14 and 20
   • No: input 3 has two outputs, 9 and 11
4. 3.

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

   • No: inputs -2 and 2 both send an arrow to 3
   • Yes: inputs -2, -1, 1, 2 and 4 each send one arrow
   • 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?

   • 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
6. 5.

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

   • No: (1, -2) and (1, 4) are on one up-and-down line
   • No: some points are below the x-axis
   • Yes: no two points are at the same height
7. 6.

   In a video game level, Pia plots where four stars sit on the grid. Is it a function, and why?

   • Yes: the points are evenly spaced along the grid
   • Yes: inputs -4, -2, 1 and 3 each have one point
   • No: the points are not on one straight line
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. 8.

   Milo prints a 12-page comic. The more pages, the longer the printing takes. Which amount is the input (independent variable)?

   • The input is the printing time
   • The input is the number of pages
   • The input is the printer
10. 9.

    Noah bakes cookies, 15 on each tray. The number of cookies depends on the number of trays. Which amount is the input (independent variable)?

    • The input is the number of cookies
    • The input is the number of trays
    • The input is the oven
11. 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