Given:
The cost of a laptop increased by 25% between 2015 and 2019.
In 2019, the laptop cost £1000.
To find:
The cost of the laptop in 2015.
Solution:
Let x be the cost of the laptop in 2015.
The cost of a laptop increased by 25% between 2015 and 2019. So, the cost of the laptop in 2019 is
Cost of laptop in 2019 = [tex]x+\dfrac{25}{100}x[/tex]
= [tex]x+0.25x[/tex]
= [tex]1.25x[/tex]
In 2019, the laptop cost £1000.
[tex]1.25x=1000[/tex]
[tex]x=\dfrac{1000}{1.25}[/tex]
[tex]x=800[/tex]
Therefore, the cost of the laptop in 2015 is £800.
