Solve Problems by Substituting Values into a Formula

In this worksheet, students will solve real life problems by evaluating a formula by substituting in the values of two unknowns.

Key stage:  KS 2

Curriculum topic:   Algebra

Curriculum subtopic:   Use Algebra Formulae

Difficulty level:

Worksheet Overview

In this activity, we will solve real life problems by substituting values with two unknowns to evaluate a formula.

Remember - To substitute just means to swap something.

Like with football - one player comes off the pitch and one comes on in their place!

They are swapped!

In maths, it looks like this with an expression:

When a = 5 and b = 10

What is the value of 2a + 4b?

2a + 4b = (2 x a) + (4 x b)

When a = 5 and b = 10 we substitute them

(2 x 5) + (4 x 10)

= 10 + 40

= 50

Let's look at a real life formula problem!

Example

The cost of hiring an electric bike is found using the following:

Cost = £4 x number of hours hired + £5 for bike lock

How much would it cost to hire a bike for 3 hours?

We substitute what we know into the problem.

We know that the bike is hired for 3 hours.

Cost = £4 x number of hours hired + £5 for bike lock
Cost = £4 x 3 hours + £5
Cost = 12 + 5
Cost = £17 for 3 hours hire

Let's try some more like this!

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