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Chapter overview
Learning goals
Learning Goals
Maths
Summary
You should be able to form expressions or formulae from information given in a question. Start by giving the unknown quantities a letter name, e.g. $x$. Then use the information in the question to create your expression or formula.
Note: Remember to substitute into the formula to check that is works.
To make an expression, read the information given, give the unknown quantity a letter name and use your knowledge of algebra to write the correct expression.
Fred is $x$ years old. George is $4$ years older than Fred. Harry is twice as old as George. Write expressions, in terms of $x$ for their ages.
Fred | $x$ |
George | $x+4$ |
Harry | $2(x+4) = 2x+8$ |
To make a formula, read the information given, give the unknown quantity a letter name and use your knowledge of algebra to give the formula.
The total cost, $C$, of a mobile phone bill is the cost of text messages, $t$, and the cost of calling, $m$. Texts are $5p$ each, and each minute of a call is $10p$. Write a formula for the cost, $C$, of the mobile phone bill.
$\underline{C= 0.05t+0.1m}$
Create a formula, as above, then substitute in for the variables in the formula to calculate the result.
A restaurant charges $£C$ for delivering pizzas, through a delivery app. They charge a standard fee of $£1.50$ and an additional $80p$ for each mile, m, travelled. Write a formula for $C$ and work out the charge for a $5$ mile delivery.
$C=0.8m+1.5$
Note: Remember to convert to the same units if necessary, in this case $80p$ has been converted to $£0.8$.
Now use the formula by substituting $m=5$ to calculate the cost.
$C = 0.8 \times 5 + 1.5 = 5.5$
The total cost is $\underline{£5.50}$
You should be able to form expressions or formulae from information given in a question. Start by giving the unknown quantities a letter name, e.g. $x$. Then use the information in the question to create your expression or formula.
Note: Remember to substitute into the formula to check that is works.
To make an expression, read the information given, give the unknown quantity a letter name and use your knowledge of algebra to write the correct expression.
Fred is $x$ years old. George is $4$ years older than Fred. Harry is twice as old as George. Write expressions, in terms of $x$ for their ages.
Fred | $x$ |
George | $x+4$ |
Harry | $2(x+4) = 2x+8$ |
To make a formula, read the information given, give the unknown quantity a letter name and use your knowledge of algebra to give the formula.
The total cost, $C$, of a mobile phone bill is the cost of text messages, $t$, and the cost of calling, $m$. Texts are $5p$ each, and each minute of a call is $10p$. Write a formula for the cost, $C$, of the mobile phone bill.
$\underline{C= 0.05t+0.1m}$
Create a formula, as above, then substitute in for the variables in the formula to calculate the result.
A restaurant charges $£C$ for delivering pizzas, through a delivery app. They charge a standard fee of $£1.50$ and an additional $80p$ for each mile, m, travelled. Write a formula for $C$ and work out the charge for a $5$ mile delivery.
$C=0.8m+1.5$
Note: Remember to convert to the same units if necessary, in this case $80p$ has been converted to $£0.8$.
Now use the formula by substituting $m=5$ to calculate the cost.
$C = 0.8 \times 5 + 1.5 = 5.5$
The total cost is $\underline{£5.50}$
Writing and using formulae
FAQs
Question: How can you check if a formula you created works?
Answer: After creating a formula, you can check it works by substituting values to make sure that the answer is as expected.
Question: How can I create a formula in algebra?
Answer: A formula can be created by analysing a questions, given in context. Letters can be used for the unknown variables to help create the formula.
Theory
Exercises
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