Let A = {1, 2, {3, 4}, 5}. Which of the following statements are false and why?
(i) {3, 4} ⊂ A 
(ii) {3, 4} ∈ A 
(iii) {{3, 4}} ⊂ A 
(iv) 1 ∈ A 
(v) 1 ⊂ A 
(vi) {1, 2, 5} ⊂A 
(vii) {1, 2, 5} ∈ A
(viii) {1, 2, 3}⊂ A 
(ix) φ ∈ A 
(x) φ ⊂ A
(xi) {φ A 

Make correct statements by filling in the symbols ⊂ or ⊄ in the blank spaces:
(i)    {2, 3, 4} ……. {1, 2, 3, 4, 5,}
(ii)   {a, b, c}……… {b, c, d}
(iii)  {x : x is a student of Class 9 of your school.} ……..{x: x is a student of your school}
(iv)  {x : x is a circle in the plane} ……..{x : x is a circle with radius 1}
(v)   {x : x is a triangle in the plane} ………. { x : x is a rectangle in the plane}
(vi)  {x : x is an equilateral triangle in the plane}……….{ x : x is a triangle in the plane}
(vii) {x : x is an even natural number} ……… {x : x is an integer}

Examine whether the following statements are true or false:
(i)  {a, b} ⊄ {b, c, a}
(ii)  {a, e} Ì { x : x is a vowel in the English alphabet.} 
(iii) {1, 2, 3} Ì {1, 2, 3}
(iv) {a} Ì {a, b, c} 
(v)  {a} Î {a, b, c} 
(vi) {x : x is an even natural number less than 6.} ⊂ { x : x is a natural number which divides 36}

Write down all the subsets of the following sets
(i) {a} (ii) { a,b} (iii) {1,2,3} (iv)

write the following intervals in set-builder form:
(i) {: R, -4 < 6}
(ii) {: R, -12 < -10}
(iii) {: R, 0 <7}
(iv) {: R, 3 4}