 # Change Missing Number Problems into Algebra (1)

In this worksheet, students express missing number problems algebraically. Key stage:  KS 2

Curriculum topic:   Algebra

Curriculum subtopic:   Express Problems Algebraically

Difficulty level:   ### QUESTION 1 of 10

When we use algebra, we use letters to stand for numbers that we are trying to find.

Algebra is like a language with its own rules.

a stands for a number.

a + 2 is 2 more than the number.

a - 7 is 7 less than the number.

5a is 5 times the number. (N.B. We don't use the × sign in algebra because it looks like the letter x.)

a/4 or ¼a is a quarter of the number or the number divided by 4. (N.B. We don't use the ÷ sign in algebra.)

Example

I think of a number.

I double it and take away 5.

I get 21.

Write this using algebra.

Use n for the number I think of.

n is the number I think of.

Double it to get 2n.

Take away 5 to get 2n - 5.

This equals 21.

So we write:

2n - 5 = 21

I think of a number.

I double it and add 5.

I get 21.

Write this using algebra.

Use n for the number I think of.

5n + 2 = 21

5n - 2 = 21

2n + 5 = 21

2n - 5 = 21

I think of a number.

I multiply it by 5 and add 2.

I get 22.

Write this using algebra.

Use n for the number I think of.

5n + 2 = 22

5n - 2 = 22

2n + 5 = 22

2n - 5 = 22

I think of a number.

I divide it by 5 and add 2.

I get 6.

Write this using algebra.

Use n for the number I think of.

5n + 2 = 6

6n + 2 = 5

n/5 + 2 = 6

5n ÷ 6 = 2

I think of a number.

I divide it by 2 and add 2.

I get 12.

Write this using algebra.

Use n for the number I think of.

2n + 2 = 12

12n + 2 = 2

n/2 - 2 = 12

½n + 2 = 12

I think of a number.

I treble it and subtract 2.

I get 16.

Write this using algebra.

Use n for the number I think of.

16n + 2 = 3

3n + 2 = 16

2n + 16 = 3

3n - 2 = 16

I think of a number.

I multiply it by 5 and subtract 5.

I get 5.

Write this using algebra.

Use n for the number I think of.

5n + 5 = 5

5n - 5 = 5

n/5 + 2 = 5

n/5 + 5 = 5

I think of a number.

I divide it by 3 and subtract 2.

I get 7.

Write this using algebra.

Use n for the number I think of.

n/3 - 2 = 7

7n + 2 = 3

n/3 + 2 = 7

7n ÷ 3 = 2

I think of a number.

I divide it by 4 and add 4.

I get 4.

Write this using algebra.

Use n for the number I think of.

4n + 4 = 4

4n + ¼ = 4

n/4 - 4 = 4

¼n + 4 = 4

I think of a number.

I divide it by 4 and add 12.

I get 12.

Write this using algebra.

Use n for the number I think of.

4n + 4 = 12

12n + 4 = 4

n/4 + 12 = 12

½n + 4 = 12

I think of a number.

I multiply it by 12 and add 12.

I get 12.

Write this using algebra.

Use n for the number I think of.

12n + 12 = n

12n - 12 = n

12n + 12 = 12

12n - 12 = 0

• Question 1

I think of a number.

I double it and add 5.

I get 21.

Write this using algebra.

Use n for the number I think of.

2n + 5 = 21
EDDIE SAYS
Double n and add 5 to get 21.
• Question 2

I think of a number.

I multiply it by 5 and add 2.

I get 22.

Write this using algebra.

Use n for the number I think of.

5n + 2 = 22
EDDIE SAYS
Five times n and add 2 to get 22.
• Question 3

I think of a number.

I divide it by 5 and add 2.

I get 6.

Write this using algebra.

Use n for the number I think of.

n/5 + 2 = 6
EDDIE SAYS
Divide n by 5 and add 2 to get 6.
• Question 4

I think of a number.

I divide it by 2 and add 2.

I get 12.

Write this using algebra.

Use n for the number I think of.

½n + 2 = 12
EDDIE SAYS
Halve n and add 2 to get 12.
• Question 5

I think of a number.

I treble it and subtract 2.

I get 16.

Write this using algebra.

Use n for the number I think of.

3n - 2 = 16
EDDIE SAYS
Multiply n by 3 and subtract 2 to get 16.
• Question 6

I think of a number.

I multiply it by 5 and subtract 5.

I get 5.

Write this using algebra.

Use n for the number I think of.

5n - 5 = 5
EDDIE SAYS
Five times n and subtract 5 to get 5.
• Question 7

I think of a number.

I divide it by 3 and subtract 2.

I get 7.

Write this using algebra.

Use n for the number I think of.

n/3 - 2 = 7
EDDIE SAYS
Divide n by 3 and subtract 2 to get 7.
• Question 8

I think of a number.

I divide it by 4 and add 4.

I get 4.

Write this using algebra.

Use n for the number I think of.

¼n + 4 = 4
EDDIE SAYS
Find a quarter of n and add 4 to get 4.
• Question 9

I think of a number.

I divide it by 4 and add 12.

I get 12.

Write this using algebra.

Use n for the number I think of.

n/4 + 12 = 12
EDDIE SAYS
Divide n by 4 and add 12 to get 12.
• Question 10

I think of a number.

I multiply it by 12 and add 12.

I get 12.

Write this using algebra.

Use n for the number I think of.

12n + 12 = 12
EDDIE SAYS
12 times n and add 12 to get 12.
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