Students will find helpful reminders in the times tables, the geometric
shapes and metric conversions.
But the thing that sets this ruler apart is the number line from -15 through 0 to 15.
It will be an invaluable tool in learning the concept of a negative number
and in understanding why equations such as -3-4 = -7, 2-8 = -6 and -3+4 = 1 are true.

I highly recommend this ruler to all teachers and students in upper
primary and lower secondary school.

Dr Brian A. Davey
Reader and Associate Professor
Mathematics, La Trobe University