Introduction to sets

Let A = { days of the week }
Find n(A).

• 4

• 5

• 7

Answer explanation

There are 7 days in a week. So n(A) = 7.

Let B = { months of the year that do not have the letter r }
List the elements with the use of { } in your response.

Let C = { factors of 12 }.

List all elements of C with the use of { }.

Let D = { positive integers less than 30 that are multiples of 4 }
Find n(D).

• 6

• 7

• 8

Let D = { positive integers less than 20 that are multiples of 4}

List all elements of D with the use of { }.

Answer explanation

{4, 8, 12, 16}

Describe J = { 1, 3, 5, 7, 9}

• prime numbers less than 11

• odd integers less than 11

• integers less than 10

Let K = { isoclese, equilateral , right-angled, scalene}
Describe K.
K is a set of ______.

L = { right angle, obtuse, acute, reflex}
L is a set of ____.

M = { 4, 8, 12, 16, ..., 40 }
M is a set of ___.

• even numbers

• multiples of 4

• multiples of 4 that are less than 41

• positive even numbers less than or equal to 40

If A = { 4, 6, 8, 10}
then
4 ∈ A.

• True

• False