From Terry Threlfall
Regarding your calculations on the salt content of Walkers crisps, how can the one significant figure in 0.4 grams per pack lead to four significant figures in 4.444 grams per day (Feedback, 14 March)? We spend a lot of time explaining the significance of significant figures to students, and professionals need to set an example. The result of a calculation should not give more significant figures than were included in the input.
The editor writes:
• You’re absolutely correct. Indeed, numerical accuracy is as important to the well-being of our youth as their salt intake. Perhaps Walkers’ confounding statistics could be used in schools as an example.
Upminster, Essex, UK
