One way to specify a set is to give a verbal description of its elements. This is known as the Descriptive form of specification.
The description must allow a concise determination of which elements belong to the set and which elements do not.
Write each of the following sets in descriptive form.
Example 1 :
V = {a, e, i, o, u}
Solution :
The given set contains vowels.
Descriptive form :
V is the set of all vowels in the English alphabet
Example 2 :
A = {1, 3, 5, 7, 9, 11, 13, 15}
Solution :
The given set contains odd numbers ending with 15.
Descriptive form :
A is the set of all odd natural numbers less than or equal to 15
Example 3 :
B = {1, 4, 9, 16, 25, 36, 49}
Solution :
The given set contains the square of natural numbers ending with 49.
Descriptive form :
C is the set of all perfect squares less than 50
Example 4 :
P = {x : x is a letter in the word "follow"’}
Solution :
The given set is in set builder form. It contains the letters of the word "follow".
Descriptive form :
P is the set of all letters in the word "follow"
Example 5 :
Q = {x : x is a prime number from 1 to 20}
Solution :
The given set is in set builder form. It contains the prime numbers from 1 to 20.
Descriptive form :
Q is the set of prime numbers in the first 20 natural numbers
Example 6 :
R = {1, 2, 3, ......, 25}
Solution :
The given set contains first 25 natural numbers.
Descriptive form :
R is the set of first 25 natural numbers
Example 7 :
R = {2, 4, 6, 8,...........}
Solution :
The given set contains positive even numbers.
Description :
R is the set of all positive even numbers
Example 8 :
S = {3, 6, 9, 12, ...................}
Solution :
The given set contains all positive multiples of 3.
Description :
S is the set of positive multiples of 3
Example 9 :
A = {234, 243, 324, 342, 423, 432}
Solution :
The given set contains three-digit numbers are formed with the digits 2, 3 and 4.
Description :
A is the set of three-digit numbers which can be formed with the digits 2, 3 and 4
Example 10 :
B = {cde, ced, dce, dec, ecd, edc}
Solution :
The given set contains all possible different arrangements of the three letters c, d and e.
Description :
B is the set of all different arrangements of the three letters c, d and e
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