Around the time of Copernicus showed that the Earth actually revolves around the Sun - mid 1500s
Around the time Sankore University and Mosque are founded at Timbuktu - 1450
Make your wild guess before opening the next section!
The Short History of the Equals Sign
If you answered 1 or 3, you're right!
Robert Recorde, a Welsh physician and mathematician, first proposed an equals sign that was basically two long parallel lines in 1557 but it didn't appear in print again until 1618, 61 years later.
Before that, there were all sorts of different ways to express equality. Most writers used words, a space, or a dash. Even after Recorde debuted the double lines to show equality, there were at least five other meanings of what we would call the equals sign.
There were other ideas for how we should express mathematical ideas. Here's a really strange one:
2|2 was the symbol for equality, 3|2 was greater than, and 2|3 was less than.
ab + ab = 2ab was written ab + ab 2|2 2ab
It wasn't until the early 1800s that the = sign was widely accepted and even then it wasn't universal. it took a long time before everyone agreed on the use of the symbol and what it means. Why can't mathematicians get along? ;-)
What the Equals Sign Doesn't Mean
So be careful how you teach it!
The equals sign means something very special to mathematicians. It signifies that two expressions are equivalent.
Unfortunately, many children start thinking that the equals sign means (insert drumroll) "Here comes the answer!"
This may seem unimportant but it is a serious barrier to understanding algebra in middle school and beyond. Students who view the right side of an equation as the answer and the left side as a problem have great difficulty solving algebraic problems. Their schema gets in the way of understanding what they're being asked to do.
What can you do?
Make sure to have the place for the answer move around in problems that you give students.
Encourage multiple solution strategies. 12 = 4 + ____ could be solved as 4 plus what equals 12 or 12 minus 4 equals what.
Play some ST Math games with the whole class and talk about an equation as a balance. Here are some to try:
First and second grade teachers - Only look at this if you are tempted to write equations for Tugboat
The bottom line is skip it on this game!
The temptation is to think about this problem as 9 ≠3.
So, we'll subtract 3 from one side and add 3 to the other side. See the problem? Remember that rule about whatever you do to one side of the equals sign you have to do to the other? The same thing holds for the signs of inequality.
If you want to record something, count all the boats and then decide how you could use that many boats total to make the two sides equal ( ___ = ___) or what number when added to itself make 12 (12 = a + a).