I’ve always been fascinated by results of calculations that seem disproportionate to the point of incredibility, but are correct. I get stroppy with people who are neither fascinated by such results nor moved to question and check them. Here are four that came to my attention recently:

• I peeled an orange and weighed the peel. It was 31% of the unpeeled fruit, so a price of $2.99/kg turns out to be $4.33/kg of the edible part.
• I read an article whose author decried the terrible devaluation of the US dollar over the past century: “A dollar in 1919 is now worth 5 cents!” That implies an average rate of inflation of 3.04%pa. A lot of central bankers would be very happy with that.
• Imagine a globe with a diameter of 30cm (1 foot in the old money) representing Planet Earth. The depth of the atmosphere would be 0.3mm – the thickness of a child’s finger nail.
• Research in the USA in 1997 found that average IQ had increased by 20 points since 1932. Eleven years later, similar research in the UK found a 14 point improvement since 1947. This is called the Flynn Effect. Other research suggests a pretty steady increase of about 3 points per decade – but only up to the late 1990s, when the trend appears to have petered out and reversed.
  [When originally posted, on 19 January, I mistyped “1970s” instead of “1990s”. Sorry.]