The obelus was first used as a symbol for division in 1659, in an algebra book by Johann Rahn. The ISO 80000-2 standard for mathematical notation recommends only the solidus / or "fraction bar" for division and that the ÷ sign "should not be used" for division.
4 RULES
How do Russians multiply?
Key questions
1. Can we confidently add or subtract integers?
2. Can we confidently multiply integers?
3. Can we confidently divide integers?
4. Can we solve problems involving the 4 rules?
5. Do we understand multiplicative reasoning?
~3 lessons
Literacy
stories that set a frame or background
stories that accompany or intertwine
stories that introduce
stories that explain
stories that ask a question
stories that entertain
Numbed! by David Lubar
Introducing...
long times short - 2
missing digits add - 4
missing digits - 2
smile division - 3
understanding the laws of arithmetic - 1, 2, 3
two digadds - 1
Developing...
long division - 3
division - 3
four operations arithmetic tasks - 1, 2, 3, 4
repunit numbers - 3
pmp arithmetic - 1, 2, 3