Counting Method / June 6, 2018 / Penelope Chow
The math and the real life everywhere require the useful skill of counting. The correct way to count something, especially, money is a very important factor of concern. It is always better to teach the children to count, before their schooling starts. To teach and make a little kid understand the method of counting is a difficult job. To make this difficult task easy, you can implement several funny methods of counting that a kid usually loves.
Like the natural numbers, Z is closed under the operations of addition and multiplication, that is, the sum and product of any two integers is an integer. However, with the inclusion of the negative natural numbers, and, importantly, 0, Z (unlike the natural numbers) is also closed under subtraction. The integers form a unital ring which is the most basic one, in the following sense: for any unital ring, there is a unique ring homomorphism from the integers into this ring. This universal property, namely to be an initial object in the category of rings, characterizes the ring Z.