# Simple Algebraic Substitution

In this worksheet, students substitute numbers for letters and work out the value of simple expressions with one variable.

Key stage:  KS 2

Curriculum topic:   Maths and Numerical Reasoning

Curriculum subtopic:   Equations and Algebra

Difficulty level:

### QUESTION 1 of 10

When we substitute a number for a letter, we simply replace the letter with the number.

However, we must remember that 4b means 4 x b.

Example

Work out the value of the following expression when a = 4

3a - 7

3a - 7

= 3 x a - 7        (3a just means 3 x a

= 3 x 4 - 7        (Change the letter into the number you are given)

= 12 - 7            (Remember BODMAS; Multiply first)

= 5

Work out the value of the following expression when a = 4

2a - 7

Work out the value of the following expression when a = 4

10 - 2a

Work out the value of the following expression when a = 4

2a + 5

Work out the value of the following expression when a = 7

2a + 6

Work out the value of the following expression when a = 7

20 - 2a

Work out the value of the following expression when a = 7

20 + 2a

Work out the value of the following expression when a = 10

20 + 2a

Work out the value of the following expression when a = 8

24 - 2a

Work out the value of the following expression when a = 10

5a + a

Work out the value of the following expression when a = 10

5a + 2 + a

• Question 1

Work out the value of the following expression when a = 4

2a - 7

1
EDDIE SAYS
2a - 7 2 x a - 7 2 x 4 -7 8 - 7 1
• Question 2

Work out the value of the following expression when a = 4

10 - 2a

2
EDDIE SAYS
10 - 2a 10 - 2 x a 10 - 2 x 4 10 - 8 2
• Question 3

Work out the value of the following expression when a = 4

2a + 5

13
EDDIE SAYS
2a + 5 2 x a + 5 2 x 4 + 5 8 + 5 13
• Question 4

Work out the value of the following expression when a = 7

2a + 6

20
EDDIE SAYS
2a + 6 2 x a + 6 2 x 7 + 6 14 + 6 20
• Question 5

Work out the value of the following expression when a = 7

20 - 2a

6
EDDIE SAYS
20 - 2a 20 - 2xa 20 - 2 x 7 20 - 14 6
• Question 6

Work out the value of the following expression when a = 7

20 + 2a

34
EDDIE SAYS
20 + 2a 20 + 2 x a 20 + 2 x 7 20 + 14 34
• Question 7

Work out the value of the following expression when a = 10

20 + 2a

40
EDDIE SAYS
20 + 2a 20 + 2 x a 20 + 2 x 10 20 + 20 40
• Question 8

Work out the value of the following expression when a = 8

24 - 2a

8
EDDIE SAYS
24 - 2a 24 - 2 x a 24 - 2 x 8 24 - 16 8
• Question 9

Work out the value of the following expression when a = 10

5a + a

60
EDDIE SAYS
If there\'s more than 1 letter, just substitute into all of them! 5a + a 5 x a + a 5 x 10 + 10 50 + 10 60
• Question 10

Work out the value of the following expression when a = 10

5a + 2 + a

62
EDDIE SAYS
5a + 2 + a 5 x a + 2 + a 5 x 10 + 2 + 10 50 + 2 + 10 62
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