Selina solutions

# Question 1

Q1) State whether or not the following elements form a set; if not, give reason:

(i) All easy problems in your text book.

(ii) All three sided figures.

(iii) The first five counting numbers.

(iv) All the tall boys of your class.

(v) The last three days of the week.

(vi) All triangles that are difficult to draw.

(vii) The first three letters of the English alphabet.

(viii) All tasty fruits.

(ix) All clever boys of class 6.

(x) All good schools in Delhi.

(xi) All the girls in your class, whose heights are less than your height.

(xii) All the boys in your class, whose heights are more than your height.

(xiii) All the problems in your Mathematics book, which are difficult for Amit.

Solution 1:

(i) No; Some problems may be easy for one person but may be difficult to some other person

(ii) Yes

(iii) Yes

(iv) No ; it is not mentioned that the boys must be taller than which boy,

If we consider three boys A, B and C ; boy B can be taller than A but not necessarily taller than C.

(v) Yes

(vi) No ; it may be difficult for one boy to draw a given triangle

But to some other boy it may be easy to draw the same triangle

(vii) Yes

(viii) No; a fruit may be tasty for one person and may not be tasty to other person/persons

(ix) No ; clever in what respect and from whom out of six ?

(x) No ; All the people can not find the same schools as good as others said .

So, the objects are not well defined

(xi) Yes

(xii) Yes

(xiii) Yes

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