Arithmetic

There are six arithmetic expressions and the number system:

• Number system
• Addition
• Subtraction
• Multiplication
• Division
• Roots
• Exponents

Digits

Numbers are made of digits. Here are their names:

0 - zero
1 - one
2 - two
3 - three
4 - four
5 - five
6 - six
7 - seven
8 - eight
9 - nine

Addition

An addition question can look like this:

  3
+ 4
----

or this:

3 + 4 = ____

(the answer is "seven", written as "7")

Worked out this is true because 3 = (equals) 1+1+1 and 4 = (equals) 1+1+1+1. Saying this it would sound like, "Three equals: one, plus one, plus one; and four equals: one, plus one, plus one, plus one."

So 3 + 4 = 1 + 1 + 1 + 1 + 1 + 1 + 1, and all of this (1 + 1 + 1 + 1 + 1 + 1 + 1) equals 7. So 3 + 4 = 7.

Multiplication table

   1   2   3   4   5   6   7   8   9  10  11  12
1  1   2   3   4   5   6   7   8   9  10  11  12
2  2   4   6   8  10  12  14  16  18  20  22  24
3  3   6   9  12  15  18  21  24  27  30  33  36
4  4   8  12  16  20  24  28  32  36  40  44  48
5  5  10  15  20  25  30  35  40  45  50  55  60
6  6  12  18  24  30  36  42  48  54  60  66  72
7  7  14  21  28  35  42  49  56  63  70  77  84
8  8  16  24  32  40  48  56  64  72  80  88  96
9  9  18  27  36  45  54  63  72  81  90  99 108