He's wrong. Some countries DO have 20 cent coins. Australia,
for example, has a 20 cent coin with Queen Elizabeth on
one side and a duckbill platypus on the other! :)
Anyway it is a trick question.
"Jane has two coins with a total value of 25 cents. If one of them
is not of 5 cents what is the other?"Jane lives in Australia. She has a 20 cent coin and a 5 cent
coin. Somebody might say to you:
"But you said one of them is not of 5 cents."
Then you answer back "Indeed, one of them IS a 5 cent coin, and
one of them IS NOT a 5 cent coin, for it is a 20 cent coin. You
mistook 'one of them' for 'neither of them'." :)
This is the Australian version of the USA trick question:
"Jane has two coins with a total value of 30 cents and one of them
is not a nickel. What coins does she have?"
Edwin