From Allan French
You entitled your article “Do the maths” (30 October, p 60) and I did. It states that 25 million (or 1 per cent) of the 25 billion red cells in my body die every day. It’s been decades since I got my degree in mathematics, but 1 per cent of 25 billion used to be 250 million. If the mathematics hasn’t changed (and I hope it hasn’t), which of the three numbers is wrong?
Claire Ainsworth writes:
• Yes, we did get our powers of 10 mixed up: 1 per cent of 25 billion is indeed 250 million; and 250 million red blood cells per day is roughly 3000 per second, not 300,000.
Londonderry, New Hampsire, US
