Mathematics
Intermediate
50 mins
Teacher/Student led
+95 XP
What you need:
IWB/Projector/Large Screen

Tables of Values: Input to Output

Explore how function machines transform numbers using rules. Build tables of input-output pairs for one-step rules, two-step rules, and decimals, then discover that one pair is not enough to identify a rule.

Teacher Class Feed

Load previous activity

    1 - Getting Started ~4 mins

    Illustration for Getting StartedPicture a machine on a conveyor belt. You drop a number in one end, the machine does the very same thing to it every single time, and a new number rolls out the other end. Today the machine's rule is × 3.

    If we drop a 4 into this × 3 machine, what number do you think rolls out the other side?

    2 - Watch and Notice ~10 mins

    Each machine takes a number in and follows a rule to give a number out. Watch the four machines in turn and see if you can work out the rule before the output appears.

    3 - Try It Together ~9 mins

    Today we work through one machine together: the × 3 machine. We will feed it numbers one at a time and write each input-output pair into a table on the board. You call out the output, we check it, and we add the row.

    Build the × 3 table

    4 - Draw the Tables in Your Copy ~3 mins

    COPYBOOK MOMENT

    Illustration for Draw the Tables in Your CopyIn your maths copy, draw a four-row input/output table for each of these four rules and fill in four pairs for that rule. Put the rule label at the top of each table.

    • × 3
    • + 5
    • × 2 then + 1
    • × 10

    5 - Work Backwards Together ~8 mins

    So far we have always known the rule and worked out the output. Now we work the other way. First we build a full table for a two-step machine, the × 2 then + 1 machine, together. Then we play detective: I will show you a pair, like input 3 gives 7, and we will try to find the rule.

    The rule today

    Here is the catch. More than one rule can turn the same input into the same output. One pair is not enough to be sure of the rule. To tell them apart, we send a second number through and check which rule still fits.

    Build and test the rules together

    6 - Class Challenge ~8 mins

    Now we work through these rules and complete a full table of four pairs for each one. The last rule is a two-step machine, and one round asks you to work backwards: given an input and its output, find the rule that fits.

    Tip

    Remember to test a second pair before you commit to a rule.

    Complete each value table

    7 - What Did We Notice? ~5 mins

    MATHS TALK

    If two different rules both give the same answer for input 3, what input could you try next to tell them apart?

    8 - What's Next ~3 mins

    What we did today

    • We saw a function machine take an input, do the same rule every time, and give an output.
    • We built tables of input-output pairs for one-step rules, two-step rules, and a decimal input.
    • We learned that one pair is not always enough to be sure of a rule, so we test a second pair.
    Coming up

    Next we turn this around fully: given a table of pairs with the rule hidden, we work out what the machine is doing.

    Pupil practice
    Module 8 · Algebra: Patterns, Expressions and Equations Algebra
    Lesson 101 · Tables of Values: Input to Output
    Download Activity Book page (PDF)
    End of lesson
    123learn · Online learning platform

    Unlock the full learning experience

    You're previewing this lesson. Get full access to this lesson and hundreds more — each one ready to teach, with interactive activities, printable resources and pupil progress tracking built in.

    Hundreds of curriculum-aligned lessons
    Interactive activities in every lesson
    Printable resources & progress tracking
    Copyright Notice
    This lesson is copyright of Coding Ireland 2017 - 2025. Unauthorised use, copying or distribution is not allowed.
    🍪 Our website uses cookies to make your browsing experience better. By using our website you agree to our use of cookies. Learn more