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Mathematics

The handy piece of maths that can help with organising chores

Should you mow the lawn first or cut the hedge? Mathematics will help you decide what to tackle first, says Peter Rowlett

By Peter Rowlett

21 May 2025

Man mowing downhill Description Man wearing white overalls and back to front baseball cap trying to mow down steep verge outside building. Memphis, USA

“Mathematically, what are we trying to optimise?”

John MacLean/Millennium Images, UK

Scheduling household chores is hard. Say you have three loads of washing: a regular load that will take 110 minutes to wash and 120 to dry; a heavily soiled load that needs an extra 30 minutes to wash; and a sensitive one that will take 130 minutes to wash and 160 to dry. In which order do you wash them?

In the branch of applied maths known as operational research, this is called a two-machine problem. Lots of businesses have similar issues. One approach, to find the shortest overall…

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