Roster method Or Tabular Form
In this method, we represent a set by listing all its elements between braces
Example.–1) The set X of the vowels of the English alphabet is represented as X = { a, e, i, o, u }
Example.-2) the set X of the days of a week is represented as X = { Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday }
Example.-3) The set X of the month of a year is represented as X = { January, February, March, April, May, June, July, August, September, October, November, December }
The order in which we list the elements of a set within braces is immaterial. Thus each of the following denotes the same set,
{ a, b, c }, { b, a, c }, { a, c, b }, { c, a, b }, { c, a, b }, { b, c, a }
In listing the elements of a set in the tabular form, we do not repeat any elements. Thus, if ‘Y’ is the set of digits in the number 324, 4512, 1234, 458, 875, 8426 then Y = { 3, 2, 4, 5, 1, 8, 7, 6 }
Write each of the following sets in the Roster Form or Tabular Form
1) The set of the months in a year that end with y
Ans.) If ‘Y’ is the set of month of the year-end with y then the set is –
Y = { January, February, May, July } (Ans.)
2) Find the set of the months in a year that has 30 days
Ans.) If ‘A’ is the set of the months of the year which has 30 days, then the desired set would be –
A = { April, June, September, November } (Ans.)
3) Find the set of the odd numbers between 20 to 40,
Ans.) If ‘X’ is a set of the odd number between 20 to 40, then
X = { 21, 23, 25, 27, 29, 31, 33, 35, 37, 39 } (Ans.)