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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?
Answer
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
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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?
Answer
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!
