A worker received a 10% pay increase in 2017 and a further 10% pay increase in 2018 - OCR - GCSE Maths - Question 19 - 2021 - Paper 1

In 2018, the worker receives another 10% increase based on the new salary from 2017. So, the salary after the second increase is:

$S_{2018} = S_{2017} + 0.1S_{2017} = 1.1S + 0.1(1.1S) = 1.1S + 0.11S = 1.21S$

To find the total percentage increase over the original salary $S$, we first find the new salary:

$ext{Total Increase} = S_{2018} - S = 1.21S - S = 0.21S$

Next, we convert this into a percentage of the original salary:

ext{Percentage Increase} = rac{0.21S}{S} imes 100 ext{%} = 21 ext{%}