How much energy does Britain use - and how much could we generate without burning fossil fuels?
Physics professor David MacKay has been doing the sums.
He has added up everything we need and everything we could produce sustainably.
He says we can live within our means - but only if we are prepared to make huge changes.
Giving it 110%
Fired? Maybe they should have given it more than 100%.
There was a time when you could count on numbers not to get above themselves - when 100% percent was the largest possible proportion of something.
But then linguistic inflation set in.
If you are not pledging to put in 110% effort, you are just not trying hard enough.
Where will it end?
Our reporter Chris Bowlby finds out.
Explaining the Debt
Is government borrowing low or high by international standards?
If the British government was just one person, how much money would they owe?
This week we were bombarded by Budget figures so staggeringly large it was almost impossible to understand what they meant.
But we think we have found a way to explain exactly where Britain stands.
First, Tim had to declare himself dictator-for-life.
If you like that, you will probably like
Would you use "personal informatics" to log your sex life?
The latest internet trend is something called "personal informatics" - sites that allow users to track their personal data in the hope some useful pattern might emerge.
So, sensing an opportunity, we asked Tim to use such a site in an attempt to improve his own productivity.
See how he is getting on
BBC Radio 4's More or Less
is broadcast on Friday, 24 April at 1330 BST and repeated on Sunday, 26 April at 2000 BST.
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