On July 29, 1818, Gaspard Monge, French mathematician, died in Paris. You can read about his life and how it was affected by the French Revolution here. However, this blog is not about Monge. I mention him only because the fact of his passing reminded me of the fun Frances Rolleston had with French mathematics.
A French nobleman who had fled the Revolution tutored her in French and mathematics. The system he taught her was later adopted in English universities, but before it was widely known, Frances had fun stumping her acquaintances with problems which now seem simple to us.
The following is from a letter she wrote some time after the events.
My French friend despised English mathematics. He told me to try my professing friends with these two questions; first, what is two-thirds of three-fourths? It was curious to see gentlemen who had taken their degree, fill quantities of paper, and come to no satisfactory answer. One clergyman, who was trying to puzzle a young disciple of mine studying for college, could not master this simple problem. Then said I, try another, of which my French friend had said, 'No Englishman can do this'—'PROVE that two and two make four." After making his wife and young cousin laugh at his failure, he gave it up, and I was obliged to show him the French proof.
Some time later when Frances told this story to a new college graduate, he said, "We know that now, we are taught on the French plan." So the English have at least this to thank the French for.