The Handy Math Answer Book

What does carrymean in addition?

In addition, carrydefines a way in which larger numbers are added. In this arithmetic

operation, there is a shifting of leading digits into the next column to the left when

the sum of that column exceeds a single digit. For example, carrying is evident in the

following operation in the base 10 numbering system (adding addends 234 and 168,

giving the sum 402):

By adding the same columns, starting in the right-hand column, 8 4 is 12, a num-

ber larger than 9, the highest number than can exist in that spot; carry the amount of ten

to the next column, leaving 2; add 3  6 1 (which, when carried, represents 10 for this

column), which equals 10, again a number larger than 9. Again, carry the one to the next

column leaving 0; adding the 2  1 1 (carried) equals 4. All total, the sum is 402.

How do you subtract numbers?

Subtraction is the “opposite” (or, in set theory, the inverse) of addition: In its simplest

form, one whole number is essentially taken away from another whole number. When

you subtract numbers, you are answering the question of how many are left. For

example, if 23 people leave a building that has 123 people (123 23), there would be

100 people left in the building.

What does borrowmean in subtraction?

As with “carry” in addition, to “borrow” in subtraction means to take amounts from

one number and assign them to the next. In this procedure, the 10 is borrowed from

402

168

234

11

+

92

When was the equal sign introduced into mathematics?

T

he equal sign () is a relatively new invention in mathematics. It was first

used by British mathematician Robert Recorde (1510–1558; also seen erro-

neously as Record) in his book The Whetstone of Witte(1557), the first algebra

book introduced in England. In it he justifies using two parallel line segments

“bicause noe 2 thynges can be moare equalle (sic)” (“because no two things can

be more equal than parallel lines.”) It was not an immediately popular symbol,

though, with mathematicians continuing to use a range of symbols for equal,

including the two parallel lines (||) used by Wilhelm Xylander in 1575, and aeor

oe(both from the word aequalis,the Latin for “equal”). But for the most part,

the word “equal” was written in an equation until around 1600, when Recorde’s

symbol became more readily accepted, and it continues to be so today.