# Problems from The set of the natural numbers, order and representation

Which of these numbers are natural?

a) $$2.3$$

b) $$80$$

c) $$2$$

d) $$-12$$.

See development and solution

### Development:

a) Can we say: "I have $$2.3$$ brothers?"" No, perhaps we have two brothers, perhaps three, but we can nothave $$2.3$$.

b) In this case you can say, for example: "In this field there are $$80$$ sheep." Therefore, it is a natural number.

c) As in the previous case, it can be used to count things, "My brother is two years old." That is to say, it is also a natural number.

d) This is not for counting objects: "Tomorrow $$-12$$ guests will visit us!" is not correct.

### Solution:

$$2.3$$ is not a natural number.

$$80$$ is a natural number.

$$2$$ is a natural number.

$$-12$$ is not a natural number.

Hide solution and development

Write, using the symbols $$<$$ and $$>$$, the following sentences:

a) $$5$$ is greater than $$3$$

b) $$2$$ is less than $$7$$

c) $$4$$ is greater than $$5$$

See development and solution

### Development:

a) $$5$$ is greater than $$3$$ is the same as $$5 > 3$$.

b) $$2$$ is less than $$7$$ is the same as $$2 < 7$$.

c) We can write $$4 > 5$$, but it's not true because $$4$$ isn't greater than $$5$$.

### Solution:

a) $$5 > 3$$

b) $$2 < 7$$

c) $$4$$ is greater than $$5$$ can be translated to $$4 > 5$$, which is false.

Hide solution and development