Millions, Billions, Trillions and Millillions

Here’s a bit of history about the words we use for numbers big enough to describe world populations and budgets.

Continue reading Millions, Billions, Trillions and Millillions

Two, One, Zero, Blast Off! (or, How To Teach Subtraction)

Last week, I got to help my son learn subtraction with borrowing. He’s already learned how to subtract two-digit numbers when borrowing is not needed, as you can see from the picture below.

Continue reading Two, One, Zero, Blast Off! (or, How To Teach Subtraction)

7 Is Not Prime, and Fermat’s Last Theorem

I was reading a book about numbers recently, and almost put it down when it started talking about prime numbers. The author had tried to work out the prime factors of 72, got as far as 2 x 2 x 2 x 9, then said “you guessed it, 9 is a prime number!” Arrgh!

Continue reading 7 Is Not Prime, and Fermat’s Last Theorem