### Practice Set 1.1 Sets Class 9th Mathematics Part I MHB Solution

###### Practice Set 1.1

Question 1.

Write the following sets in roster form.

i. Set of even numbers

ii. Set of even prime numbers from 1 to 50

iii. Set of negative integers

iv. Seven basic sounds of a sargam (sur)

Answer:

We know that in roster method, we write all the elements of a set in curly bracket. Each of the element is written only once and separated by commas. The order of an element is not important but it is necessary to write all the elements of the set.

i. A = {2, 4, 6, 8, 10, 12, 14, … }

ii. B = {2}

iii. C = { … -7, -6, -5, -4, -3, -2, -1}

iv. D = {Sa, Re, Ga, Ma, Pa, Dha, Ni}

Question 2.

Write the following symbolic statements in words.

i. 4/3 ∈ Q

ii. - 2 N

iii. P = {P is an odd number}

Answer:

i. We know that Q is denoted as set of rational numbers.

We write 4/3 ∈ Q as ‘4/3 is an element of set of rational numbers’.

ii. We know that N is denoted as set of natural numbers.

We write -2 N as ‘-2 is not an element of set of natural numbers.’

iii. We write P = {p| p is an odd number} as ‘Set P contains all the odd numbers’.

Question 3.

Write any two sets by listing method and by rule method.

Answer:

We know that in listing method, we write all the elements of a set in curly bracket. Each of the elements is written only once and separated by commas. The order of an element is not important but it is necessary to write all the elements of the set and In rule method, we do not write the list of elements but write the general element using variable followed by a vertical line or colon and write the property of the variable.

Question 4.

Write the following sets using listing method.

i. All months in the Indian solar year.

ii. Letters in the word ‘COMPLEMENT’.

iii. Set of human sensory organs.

iv. Set of prime numbers from 1 to 20.

v. Names of continents of the world.

Answer:

i. We know that in listing method, we write all the elements of a set in curly bracket. Each of the elements is written only once and separated by commas. The order of an element is not important but it is necessary to write all the elements of the set.

A = {Mesa, Vrsabha, Mithuna, Karkata, Simha, Kanya, Tula, Vrscika, Dhanu, Makara, Kumbha, Mina}

ii. B = {C, O, M, P, L, E, N, T}

iii. C = {Eyes, Ears, Nose, Mouth, Skin}

iv. D = {2, 3, 5, 7, 11, 13, 17, 19}

v. E = {Asia, Africa, North America, South America, Antarctica, Europe, Australia}

Question 5.

Write the following sets using rule method.

i. A = {1,4,9,16,25,36,49,64,81,100}

ii. B = {6,12,18,24,30,36,42,48}

iii. C = {S, M, I, L, E}

iv. D = {Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday}

Answer:

We know that in rule method, we do not write the list of elements but write the general element using variable followed by a vertical line or colon and write the property of the variable.

i. A = {x| x is a perfect square number from 1 to 101}

ii. B = {y| y is a multiple of 6 and is less than 50}

iii. C = {z| z is a letter of the world ‘SMILE’.}

iv. D = {p | p is a day of the week}