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Maths · Algebra

Use a term rule

Use an algebraic rule to calculate a named sequence term.

Watch the worked example

Unlock Any Sequence Term

This video shows how to use a rule written with letters to calculate a named term in a number sequence. Watch an 11+ maths question solved step by step.

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Quick quiz: Use a term rule

10 questions, with feedback after each one. No sign-up needed.

Read the questions in this quiz
  1. Question 1

    The rule for this sequence is: multiply the position by 11 then subtract 8. What is the value at position 22?

    Term 1
    Value
    3
    Term 2
    Value
    14
    Term 3
    Value
    25
    Term 4
    Value
    36
    Term 5
    Value
    47
    • A.250
    • B.234
    • C.242
    • D.154
  2. Question 2

    The rule for this sequence is: multiply the position by 11 then add 6. What is the value at position 23?

    Term 1
    Value
    17
    Term 2
    Value
    28
    Term 3
    Value
    39
    Term 4
    Value
    50
    Term 5
    Value
    61
    • A.319
    • B.247
    • C.253
    • D.259
  3. Question 3

    The rule for this sequence is: multiply the position by 12 then subtract 3. What is the value at position 25?

    Term 1
    Value
    9
    Term 2
    Value
    21
    Term 3
    Value
    33
    Term 4
    Value
    45
    Term 5
    Value
    57
    • A.297
    • B.264
    • C.300
    • D.303
  4. Question 4

    The rule for this sequence is: multiply the position by 9 then add 8. What is the value at position 19?

    Term 1
    Value
    17
    Term 2
    Value
    26
    Term 3
    Value
    35
    Term 4
    Value
    44
    Term 5
    Value
    53
    • A.179
    • B.243
    • C.163
    • D.171
  5. Question 5

    The rule for this sequence is: multiply the position by 9 then subtract 3. What is the value at position 15?

    Term 1
    Value
    6
    Term 2
    Value
    15
    Term 3
    Value
    24
    Term 4
    Value
    33
    Term 5
    Value
    42
    • A.135
    • B.138
    • C.132
    • D.108
  6. Question 6

    The rule for this sequence is: multiply the position by 11 then add 16. What is the value at position 12?

    Term 1
    Value
    27
    Term 2
    Value
    38
    Term 3
    Value
    49
    Term 4
    Value
    60
    Term 5
    Value
    71
    • A.116
    • B.148
    • C.308
    • D.132
  7. Question 7

    The rule for this sequence is: multiply the position by 9 then add 14. What is the value at position 12?

    Term 1
    Value
    23
    Term 2
    Value
    32
    Term 3
    Value
    41
    Term 4
    Value
    50
    Term 5
    Value
    59
    • A.234
    • B.122
    • C.94
    • D.108
  8. Question 8

    The rule for this sequence is: multiply the position by 11 then add 4. What is the value at position 27?

    Term 1
    Value
    15
    Term 2
    Value
    26
    Term 3
    Value
    37
    Term 4
    Value
    48
    Term 5
    Value
    59
    • A.293
    • B.301
    • C.297
    • D.341
  9. Question 9

    The rule for this sequence is: multiply the position by 11 then add 18. What is the value at position 24?

    Term 1
    Value
    29
    Term 2
    Value
    40
    Term 3
    Value
    51
    Term 4
    Value
    62
    Term 5
    Value
    73
    • A.246
    • B.462
    • C.264
    • D.282
  10. Question 10

    The rule for this sequence is: multiply the position by 6 then add 17. What is the value at position 19?

    Term 1
    Value
    23
    Term 2
    Value
    29
    Term 3
    Value
    35
    Term 4
    Value
    41
    Term 5
    Value
    47
    • A.97
    • B.131
    • C.216
    • D.114

Practise it now

Work out which two gears turn these numbers into those numbers.

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A worked example

One question of the kind this skill is tested with, worked all the way through: the reasoning, and what the wrong answers are there to catch.

Using a supplied term rule

The rule for this sequence is: multiply the position by 3 then add 8. What is the value at position 10?

The table checks the rule: every listed position follows it.

Term 1
Value
11
Term 2
Value
14
Term 3
Value
17
Term 4
Value
20

Data table with columns Position, Value. Rows: Position Term 1, Value 11; Position Term 2, Value 14; Position Term 3, Value 17; Position Term 4, Value 20.

Table columns: Position, Value. Rows: Term 1, 11; Term 2, 14; Term 3, 17; Term 4, 20.

  1. 54
  2. 38
  3. 22
  4. 30

Answer: 38

How you get there

The rule multiplies the position first, so 3 x 10=30, and adding 8 gives 38, which means position 10 holds 38.

Why the other answers tempt

The two steps are not interchangeable: multiplying after the second step gives a different value.

If they are stuck, say this

Do the multiplication first and the addition second - check the rule on one of the rows in the table before you use it.

Now do it live in Function Machine

What this exercise is doing

Function Machine

Work out which two gears turn these numbers into those numbers.

A function machine does the same thing to every number that enters it. You found the rule backwards - from the outputs - which is inverse thinking. And the order of the gears is part of the rule: ×3 then +1 turns 2 into 7, while +1 then ×3 turns the same 2 into 9. Same gears, different machine.

  1. Step 1. Deduce the gears. Drag gears into the machine so every ticket comes out right.
  2. Step 2. Run it. New number going in. Predict the output BEFORE you pull the lever.

What to say if they get stuck

  1. Look at 2 → 7 and 4 → 13. When the input goes up by 2, the output jumps by 6. What multiplies by 3?
  2. Try ×3 first: 2 becomes 6, but the ticket says 7. What tiny gear finishes the job?
  3. The order of the gears changes the answer. ×3 then +1 gives 7; +1 then ×3 gives 9.

Open Function Machine on its own page to share it

How use a term rule differs from the skills beside it

The same exercise practises several skills, and telling them apart is often the difficulty rather than the exercise itself. On this page the skill is: use an algebraic rule to calculate a named sequence term, and it stops where rule is supplied.

Questions parents ask about use a term rule

What this skill involves, common mistakes and ways to practise it at home.

Use an algebraic rule to calculate a named sequence term. It is one of 55 named maths skills in the 11+, in the algebra strand, and this page carries 1 interactive exercise that practises it.

Knowing which maths topic to practise is most of the work

A free diagnostic covers arithmetic, fractions, geometry, measure and data handling, and comes back with the topics to spend the next few weeks on.