# A2a – Substituting numerical values into formulae and expressions

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Prerequisites

# Substituting numerical values into formulae and expressions

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1. Find a possible value of $$n$$ so that $$n+7$$ is less than $$2n$$.
2. Find a possible value of $$n$$ so that $$n+7$$ is more than $$2n$$.
3. Find the value of $$n$$ such that $$n+7=2n$$.

1. Find a possible value of $$x$$ so that $$x+8$$ is less than $$3x$$.
2. Find a possible value of $$x$$ so that $$x+8$$ is more than $$3x$$.
3. Find the value of $$x$$ such that $$x+8=3x$$.
4. Can you find the value of $$x$$ such that $$x+7=3x$$?

1. Find a set of values of $$p$$, $$q$$, and $$r$$ such that $$\dfrac{p+q}{r}=1$$, where $$p$$, $$q$$, and $$r$$ are positive integers.
2. Find a different set of values of $$p$$ $$q$$, and $$r$$ such that $$\dfrac{p+q}{r}=1$$, where $$p$$, $$q$$, and $$r$$ are positive integers.
3. Find a set of values of $$p$$, $$q$$, and $$r$$ such that $$\dfrac{p+q}{r}=1$$ and $$p+q+r=25$$.
Teacher resources

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In the real world

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What next?
Substitution is a fundamental skill in algebra, along with solving equations. You will use it in many contexts. Two basic situations in which you will use substitution are (1) to plot a graph given its equation and (2) to use formulas to work out some useful information, such as the area of a shape: