A letter to the Sheffield Star
As someone who teaches maths for a living it saddens me when I see mathematical errors in your paper.
In a letter about Council Tax increases (21.2.18) Ron Sanderson claimed that last year’s 5.99% rise combined with this year’s 4.99% rise made a total increase of 10.98%. He has added the percentages, ignoring the fact that this year’s increase is 4.99% more than the new total for last year.
For every 100p you paid in Council Tax in 2016, you paid 100 x 1.0599 in 2017.
In 2018 you will pay 100 x 1.0599 x 1.0499 which equals 111.28p or an increase of 11.28%
Understanding percentages is vital when working out things like Council Tax rises, pay claims, credit agreements or interest earnt on investments. People who don’t understand percentages and APR’s are much more likely to be ripped off. If you need help with maths visit my website at www.mathswithgraham.org.uk where you will find free activities, some with a Sheffield theme such as the Sheaf Valley Maths Trail, to help people of all levels, from the very basic up to Higher GCSE.
Maths with Graham
Here is the original letter.