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Year 7

Substituting particular values

I can substitute particular values into a generalised algebraic statement to find a sense of how the value of the expression changes.

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New

Year 7

Substituting particular values

I can substitute particular values into a generalised algebraic statement to find a sense of how the value of the expression changes.

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Share activities with pupils

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Lesson details

Key learning points

Expressions and formulae in context can be evaluated for particular values.
Changing the value of the letter changes the expression.
Exploring what values give a particular solution can help understand the expression.
Expressions may have multiple variables and we can substitute some or all of them for numbers.

Keywords

Substitution - Substitute means to put in place of another. In Algebra, substitution can be used to replace variables with values.

Common misconception

Pupils may struggle with exponents especially which value to square when variables have coefficients

Reminder of priority of operations and the exponent acts on the value it is directly preceded by.

You may which to explore calculator use including squaring a negative on a calculator and the use of brackets. Get students familiar with using arrow keys to change the values they are substituting. An emulator or visualiser might be useful.

Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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Worksheet

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Starter quiz

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6 Questions

Q1.

Calculate $$(-5)^2$$

Correct Answer: 25, twenty five

Q2.

Select the correct first step to evaluate $$ 2+3\times 5^2$$

$$2+3=5$$

$$3\times 5= 15$$

Correct answer: $$5^2=25$$

Q3.

Evaluate $${12\times 2\over 4}-2$$

Correct Answer: 4, four

Q4.

Starting with the first step, put these lines of working in order to show how to evaluate $${25+2\times (2+1)^2\over 10}-4$$

1 - $${25+2\times 3^2\over 10}-4$$

2 - $$ {25+2\times 9\over 10}-4$$

3 - $$ {25+18\over 10}-4$$

4 - $$ {43\over 10}-4$$

5 - $$ 4.3-4$$

Q5.

In the equation $$2a+1=5-3a$$, $$5-3a$$ is called an .

Correct Answer: expression

Q6.

Match up the directed number calculation with the correct value.

Correct Answer:$$(-10)^2$$,100

100

Correct Answer:$$-10\times 2$$,-20

-20

Correct Answer:$$-10\times -2$$,20

Correct Answer:$$2-10$$,-8

-8

Correct Answer:$$2--10$$,12

Correct Answer:$$-2--10$$,8

Exit quiz

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6 Questions

Q1.

To evaluate an expression for a given value of its variable we can the value in place of the variable

Correct Answer: substitute

Q2.

Match up the expressions with their value when $$r=7$$

Correct Answer:$$r+50$$,57

Correct Answer:$$r^2$$,49

Correct Answer:$$6r$$,42

Correct Answer:$$r-1$$,6

Correct Answer:$$2r-10$$,4

Correct Answer:$$ r+1\over 4$$,2

Q3.

For what value of $$y$$ does $$3y$$ have the same value as $$y+6$$? $$y=$$

Correct Answer: 3, three

Q4.

For which values of $$y$$ is $$y^2-3$$ smaller than $$y$$?

Correct answer: 0

Correct answer: 2

-3

Correct answer: -1

Q5.

For the values of $$a, b$$ and $$c$$ shown evaluate the expression $$2ab-c$$

Correct Answer: 26, twenty six, twenty-six

Q6.

For the values of $$a, b$$ and $$c$$ shown evaluate the expression $$(2a)^2-bc$$

Correct Answer: 112