Addition of natural numbers matches combining finite collections and is written a+b; the sum does not depend on the order in which we count objects.
Properties of addition:
- Commutative: a+b=b+a.
- Associative: (a+b)+c=a+(b+c) — parentheses show which addends you add first.
- Zero: a+0=a and 0+a=a.
Subtraction is the inverse of addition: if a+b=c, then c−a=b and c−b=a. The difference a−b is the number x such that b+x=a.
Check subtraction: add the difference and the subtrahend — you should get the minuend.
For multi-digit numbers, columns are convenient: work place by place with carrying when you add and regrouping when you subtract.
a+b=b+a — order of addends does not matter
(a+b)+c=a+(b+c) — grouping addends
Subtraction ties to addition: a+b=c⇒c−a=b
In columns — place by place, carry and regroup
Column addition (no carry in a column)
Content is available with subscription.
Get full access to all courses on the platform for one year with a single payment.
▼
Unlike other platforms that charge per course, here you get everything for one price, and after one year of use there will be no automatic charge for the following year.