Substitution

Substitute values into algebraic expressions and formulas to evaluate them.

Worked examples

Substituting into a one-variable expression

Straightforward

Problem

x = 4

, find the value of

3x - 5

Substituting into a two-variable expression

Moderate

Problem

a = 3

and

b = -2

, find the value of

2a + b^2

Substituting into a formula

Challenging

Problem

The area of a triangle is given by the formula

A = \dfrac{1}{2}bh

. Find

A

when

b = 10

and

h = 6

Practise

Q1·Straightforward

x = 3

, find the value of

2x + 5

Q2·Straightforward

n = 4

, find the value of

3n - 2

Q3·Straightforward

a = -2

, find the value of

5a + 1

Q4·Straightforward

m = 6

, find the value of

\dfrac{m}{2} + 4

Q5·Moderate

x = 3

and

y = 2

, find the value of

4x - 3y

Q6·Moderate

a = 5

and

b = -1

, find the value of

2a + 3b

Q7·Moderate

p = 4

and

q = 3

, find the value of

p^2 - q

Q8·Moderate

x = -2

and

y = 5

, find the value of

xy - x

Q9·Challenging

The area of a rectangle is given by

A = lw

. Find

A

when

l = 8

and

w = 5

Q10·Challenging

The perimeter of a rectangle is given by

P = 2l + 2w

. Find

P

when

l = 9

and

w = 4

Q11·Challenging

The average speed formula is

v = \dfrac{d}{t}

. Find

v

when

d = 120

and

t = 3

Q12·Challenging

The formula

C = \dfrac{5(F - 32)}{9}

converts Fahrenheit to Celsius. Find

C

when

F = 77