Write the following sets in the roster form:

(i) A = {x | x is a month of a year having 30 days}

(ii) B = {x | x = 2n, n ∈ W and n < 5}

(iii) C = {x | x ∈ N and x² < 40}

(iv) D = {all letters in the word PERMISSION}

(v) E = {x : x ∈ I and x² < 10}

(vi) F = {x : x ∈ N, 15 < x < 50 and x is divisible by 6}

(vii) the set of whole numbers which are greater than 14 and divisible by 7

(viii) the set of signs of four fundamental operations of arithmetic.

(i) The months of a year having 30 days are April, June, September and November.

A = {April, June, September, November}

(ii) B = {x | x = 2n, n ∈ W and n < 5}

The whole numbers less than 5 are 0, 1, 2, 3 and 4.

When n = 0, x = 2 × 0 = 0

When n = 1, x = 2 × 1 = 2

When n = 2, x = 2 × 2 = 4

When n = 3, x = 2 × 3 = 6

When n = 4, x = 2 × 4 = 8

B = {0, 2, 4, 6, 8}

(iii) C = {x | x ∈ N and x² < 40}

For x = 1, x² = 1 < 40 ✓

For x = 2, x² = 4 < 40 ✓

For x = 3, x² = 9 < 40 ✓

For x = 4, x² = 16 < 40 ✓

For x = 5, x² = 25 < 40 ✓

For x = 6, x² = 36 < 40 ✓

For x = 7, x² = 49 > 40 ✗

C = {1, 2, 3, 4, 5, 6}

(iv) The letters in the word PERMISSION are P, E, R, M, I, S, S, I, O, N. Writing each letter only once, we get P, E, R, M, I, S, O, N.

D = {P, E, R, M, I, S, O, N}

(v) E = {x : x ∈ I and x² < 10}

For x = 0, x² = 0 < 10 ✓

For x = ±1, x² = 1 < 10 ✓

For x = ±2, x² = 4 < 10 ✓

For x = ±3, x² = 9 < 10 ✓

For x = ±4, x² = 16 > 10 ✗

E = {-3, -2, -1, 0, 1, 2, 3}

(vi) F = {x : x ∈ N, 15 < x < 50 and x is divisible by 6}

The natural numbers between 15 and 50 that are divisible by 6 are 18, 24, 30, 36, 42 and 48.

F = {18, 24, 30, 36, 42, 48}

(vii) The whole numbers greater than 14 and divisible by 7 are 21, 28, 35, 42, 49, ……

The required set = {21, 28, 35, 42, 49, ……}

(viii) The four fundamental operations of arithmetic are addition, subtraction, multiplication and division. Their signs are +, -, × and ÷ respectively.

The required set = {+, -, ×, ÷}