Posted by: Alexandre Borovik | March 5, 2009

## A childhood story: BC

I could not understand the “invert and multiply” rule for dividing fractions. I could obey the rule, but why was multiplying by $4/3$ the same as dividing by $3/4$?

My teachers could not explain, but I was used to that. I couldn’t work it out for myself either, which was less usual.

Finally I asked my father, who was an accountant. He said: if you divide everything into halves, you have twice as many things. Suddenly not just fractions but the whole of algebra made sense for the first time.

My final point was that i suddenly also understood that $a/b$ really was the result of dividing $a$ by $b$, as well as the instruction to do it.