The Number System

Question 1

What are natural numbers?

Answer 1

All positive numbers without zero

Question 2

What are whole numbers?

Answer 2

All positive numbers with zero

Question 3

What are integers?

Answer 3

All negative and positive numbers

Question 4

What are rational numbers?

Answer 4

All numbers that can be written as a fraction

Question 5

What are irrational numbers?

Answer 5

All numbers that can’t be written as a fraction

Question 6

What are real numbers?

Answer 6

All numbers

Question 7

What does ∈ mean?

Answer 7

Belongs to

Question 8

What does ∉ mean?

Answer 8

Doesn’t belong to

Question 9

What is a cardinality and how is the cardinality of set A (ex) written?

Answer 9

It’s the number of elements in a set. Ex: n(A)

Question 10

What does {} or Ø mean?

Answer 10

Empty set

Question 11

What does ⊆ mean?

Answer 11

Subset

Question 12

What is the formula to find the number of subsets of a set?

Answer 12

2^n, where n is the number of elements in the set

Question 13

What is the universal set?

Answer 13

The set that contains all sets being considered

Question 14

What is the formula to find the number of proper sets of a set?

Answer 14

2^n - 1, where n is the cardinality of the set

Question 15

What is a proper set?

Answer 15

When two sets aren’t equal

Question 16

What is an improper set?

Answer 16

When two sets are equal

Question 17

What are the properties of real numbers?

Answer 17

1) Commutative: a + b = b + a
2) Associative: a + (b + c) = (a + b) + c
3) Identity: 0 for addition, 1 for multiplication
4) Inverse: +) a -> -a x) a -> a^-1 or 1/a
5) Distributive: a (b + c) = ab + ac

Question 18

What does ≈ mean?

Answer 18

Approximately

Question 19

How can you tell if a number is significant or not?

Answer 19

1) Non-zero numbers are always significant
2) In-between zeros are always significant
3) Leading zeros are never significant
4) Trailing zeros are sometimes significant (if there’s a decimal)