GATE CSE
First time here? Checkout the FAQ!
x
0 votes
66 views

asked in Set Theory & Algebra by Boss (6.5k points)   | 66 views

1 Answer

+1 vote
Best answer
Answer (A) and (B).

Subset of a countable set is countable. Set of all integers is countable and hence any subset of it is also countable.

Power set of a finite set is finite and hence countable.
answered by Boss (7.9k points)  
Thank you
I doubt about A. How do you map the subset to a number line of integers?
Enumeration method:

Go in incresing order of absolute value. In a particular absolute value, go in increasing order of the value.

Start from |0| ->0.

Then |1| -> -1,1

Then |2| -> -2,2 and so on.
@GateSet

I think you meant

-1,1 -> |1|

-2,2 -> |2|

right?
Exactly
Thanks. Can you give me any good reference where the any ideas about how mappings are done is given?
As such I have no reference which I can give. I will try to find if there is any. Anyways, you an solve these type of questions intuitively.


Top Users May 2017
  1. akash.dinkar12

    3302 Points

  2. pawan kumarln

    1776 Points

  3. Bikram

    1646 Points

  4. sh!va

    1640 Points

  5. Arjun

    1396 Points

  6. Devshree Dubey

    1272 Points

  7. Debashish Deka

    1142 Points

  8. Angkit

    1044 Points

  9. LeenSharma

    1000 Points

  10. Arunav Khare

    754 Points

Monthly Topper: Rs. 500 gift card
Top Users 2017 May 22 - 28
  1. Bikram

    732 Points

  2. Arnab Bhadra

    402 Points

  3. pawan kumarln

    402 Points

  4. bharti

    304 Points

  5. LeenSharma

    238 Points


22,822 questions
29,142 answers
65,209 comments
27,666 users