A biologist has developed a blood test for detecting a certain minor abnormality in infants. Obviously if you have blood samples from 100 children, you could find out which children are affected by running 100 separate tests. But mathematicians are never satisfied by the obvious answer. Keith Ball uses information theory to explain how to cut down the number of tests significantly, by pooling samples of blood.
John Allen Paulos is the man who popularised the word "innumeracy", meaning the all-too-common condition of ignorance and bewilderment about maths and numbers in general. A light, cheerful and ever-so-slightly smug look at the problem, his best-known book of the same name (reviewed in Issue 11 of Plus) traces the roots of innumeracy to poor teaching and offers suggestions for antidotes and innoculation.
Calculus is a collection of tools, such as differentiation and integration, for solving problems in mathematics which involve "rates of change" and "areas". In the second of two articles aimed specially at students meeting calculus for the first time, Chris Sangwin tells us how to move on from first principles to differentiation as we know and love it!