Edexcel IGCSE Math A 2.3 expressions and formulae

Use this formulae page to turn contexts into algebra, substitute given values and make a specified variable the subject of a formula.

Exam points

Write formulae from contexts such as total cost, number machines or sequence rules.
Substitute values into an expression or formula before simplifying the result.
Rearrange formulae to make a named variable the subject with correct inverse operations.

Covered syllabus points

2.3.A Unknowns and variables 2.3.B Correct notational conventions for algebraic 2.3.C Substitution in expressions and formulae 2.3.D Formulae from mathematics and other real-life contexts 2.3.E Derive a formula or expression 2.3.F Changing the subject of a formula 2.3.HA Advanced changes of subject

[Maximum number: 2]

Work out the value of w when y=-2

$5(-2)^2-(-2)^3=20-(-8)=28$
Final answer: 28

[Maximum number: 2]

In a warehouse there are two types of shelves, type R and type S.
These two types of shelves are arranged into shelving units that form a sequence of patterns.
Here are the first three terms in the sequence.

Figure for Question 2.3 Expressions and formulae question 2 — Edexcel IGCSE Math A Higher

Diagram NOT accurately drawn

The width of each type R shelf is 2.4 m and the width of each type S shelf is 3.5 m

Find an expression for W in terms of n

Give your answer in its simplest form.

[Maximum number: 2]

Make f the subject of $m=\sqrt{\frac{1}{3} e f}$

m=\sqrt{\frac13ef}

m^2=\frac13ef

3m^2=ef

f=\frac{3m^2}{e}

Final answer:

f=\frac{3m^2}{e}

M1 oe must have f=.

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Covered syllabus points

2.3 Expressions and formulae question 1

2.3 Expressions and formulae question 2

2.3 Expressions and formulae question 3