Substitution: a letter stands for a number

The Maths Habit Handout to print

This box has a number inside. What could it be?

a4? 7? 100?

Any number. Once we know it, we can use it.

Letter
Stands for a number.
Substitute
Put a number in place of a letter.
Expression
Numbers and letters joined by +, − and × signs.
Formula
A rule that works something out.

3×a4+2=14
  1. Put the number in the box.3a means 3 × a: write the × back in.
  2. Then work it out.Times first, then add or take away.

What does it mean?

3a 3 × a

What does it mean?

5b 5 × b

a = 5Work out a + 6.
Put the number in the box.
Then work it out. 11

a+6=511

b = 8Work out b − 3.
Put the number in the box.
Then work it out. 5

b8−3=5

a = 5Work out a + 6.
Put the number in the box.
Then work it out. 11

a+6=511

c = 4Work out 12 − c.
Put the number in the box.
Then work it out. 8

12−c=48

a = 5Work out a + 6.
Put the number in the box.
Then work it out. 11

a+6=511

n = 2Work out n + 7.
Put the number in the box.
Then work it out. 9

n2+7=9

a = 5Work out a + 6.
Put the number in the box.
Then work it out. 11

a+6=511

a = 3Work out 4a.
Put the number in the box.
Then work it out. 12

4×a=312

a = 5Work out a + 6.
Put the number in the box.
Then work it out. 11

a+6=511

y = 6Work out 2y − 5.
Put the number in the box.
Then work it out. 7

2×y−5=67

Substitution: a letter stands for a number worksheet, page 1

What does it mean?

2a + b 2 × a + b

cost = 4 × tickets. What goes in the box for 5 tickets?

4×tickets5 5

a = 3, b = 4Work out 2a + b.
Put the number in the box.
Then work it out. 10

2×a+b=3410

x = 5, y = 2Work out x + 3y.
Put the number in the box.
Then work it out. 11

x5+3×y=211

a = 3, b = 4Work out 2a + b.
Put the number in the box.
Then work it out. 10

2×a+b=3410

p = 6, q = 4Work out 3p − q.
Put the number in the box.
Then work it out. 14

3×p−q=6414

Substitution: a letter stands for a number worksheet, page 2

Answer sheet

a = 4. Thumbs up: right. Thumbs down: wrong.

  1. a + 2 = 6

    Right

  2. 3a = 34

    Wrong: 12

  3. 2a = 8

    Right

  4. a − 1 = 5

    Wrong: 3

  5. 5a = 20

    Right

  1. a = 1. Which is bigger, 3a or a + 3?

    a + 3: 4 is more than 3

  2. 3a = 21. What number is a?

    7

  3. Write an expression with a that makes 10 when a = 2.

    5a, or a + 8

  1. a = 5. Work out a + 7.

    12

  2. a = 4. Work out 3a.

    12

  3. a = 3, b = 2. Work out 2a + b. Put the number in the box. Then work it out.

    8
    2×a+b=
Exit tickets to print