On July 8 the rate of inflation in Zimbabwe was reported to have reached 2.2 million per cent. At this rate, how long would it take for the Z$100 billion loaf of bread to double in price? If true, does this constitute a world record?

Your correspondent asks how soon a commodity would double in price under an annual inflation rate of 2.2 million per cent. The answer is 25.3 days (=log2/log20001 of a year).

Roy McKenzie, Holbrook, Derbyshire

According to Wikipedia, the world record for inflation was in postwar Hungary with a monthly rate that peaked at 41.9 quadrillion per cent, which converts to an effective annual rate that is a number so large it probably doesn’t have a name — 2.92 x 10 to the power of 177 per cent.

Ian Wright, Isle of Man

Why are magnets nearly always depicted as horseshoe-shaped? I seem to remember at school, many years ago, that they were generally oblong.

For educational purposes, such as school physics, the bar-shape magnet is often preferred as many aspects of magnetism can be easily studied. The horseshoe-shaped magnet is convenient as an instantly recognisable icon and so is often used to represent a magnet.

Peter Neufeld, Sidcup, Kent

Bar magnets have their uses but practical (horseshoe-shaped) magnets are more often used to pick things up and for this you need the magnetic poles physically close together to ensure the greatest magnetic attraction

Brian Frost, Ferndown, Dorset

Is there a traceable reason why the names “birdie” and “bogey” appear in the golfing lexicon?

Birdie was in fact an American colloquialism and refers, of course, to “bird”, where it described a first-rate animal or thing, including golf.