[Aptitude] Family Trees & Blood Relations: Logical Arrangement Made Easy

[Aptitude] Family Trees & Blood Relations: Logical Arrangement Made Easy

  1. Introduction
  2. Dataset #1
    • Step 1: Gender and Generation table
    • Step 2: Checklist
    • Questions based on the Family-Data
  3. Dataset #2: UPSC CSP’2000
    • Step #1: Gender and Generation table
    • Step-2: Run the checklist
    • Step-3: Solve the Question
  4. Do eliminate wrong options
  5. Keep a Watch on the Watch
  6. Previous Articles on Aptitude

Introduction

  • Family relation / Family tree / Bloodline related aptitude questions are pretty common in CSAT, CMAT, IBPS and CAT.

Let’s try a very clichéd and easy question.

Dataset #1

There are 6 members in a family: A to F. There are two married couples, D is grandmother of A and mother of B, C is the wife of B and mother of F, F is the granddaughter of E.
Just like our Prime Minister, There is no ‘dum’ in this sum. It requires only three simple steps.

Step 1: Gender and Generation table

  • The data talks about three things: Gender (M/F), Generation(1/2/3) and Blood Relations (mom-son etc.)
  • If you try to arrange all three of them simultaneously, it’ll only lead to frustration and wastage of time. So first concentrate on two items only: Gender and Generation. The Relations will fall in line by themselves.

Given data: D is grandmother of A and mother …..
So D is the oldest Generation and she is definitely female.
But we don’t know whether A is male / female.
Anyways fill up the Gender – Generation table

Generation Male Female Not sure(M/F)
1 Oldest D
2 Mid aged
3 Youngest A

Given data: D is grandmother of A and mother of B
Obviously “B” falls in the 2nd generation (mid-aged) but still we don’t know the gender of “B”.

Generation Male Female Not sure(M/F)
1 Oldest D
2 Mid aged B
3 Youngest A

Given data: C is the wife of B and mother of F
This one statement, tells us three things

  • C is a female and mid-aged (2nd generation)
  • B is a male.
  • F is 3rd generation. But we don’t know the Gender of “F”

Update the table with this new information

Generation Male Female Not sure(M/F)
1 Oldest D
2 Mid aged B C
3 Youngest A,F

Given data: F is the granddaughter of E
This tells us following

  • F is a female.
  • F is 3rd generation (although we knew it already.)
  • E is 1st generation and since “D” was female, this has to be male (Granddaddy).

Update the table

Generation Male Female Not sure(M/F)
1 Oldest E D
2 Mid aged B C
3 Youngest F* A

*intentional mistake.

Step 2: Checklist

  • In the arrangement questions: whether it is circular arrangement, linear arrangement or family tree: always runs the checklist after you’re done arranging the items.
  • If you had made any mistake in the arrangement, you’ll find it out at step2.
  • IF you proceed directly to solving questions, it may happen that you’ll get all answers incorrect. Because in aptitude tests, they design the 4 answers options (a/b/c/d) in such a way that even if you got incorrect arrangement, you’ll find answers matching to your arrangement!

So here is our final table

Generation Male Female Not sure(M/F)
1 Oldest E D
2 Mid aged B C
3 Youngest F A

And here is our checklist from the given question data

Checklist Pass/Fail
There are two married couples Pass
D is grandmother of A and mother of B Pass
C is the wife of B and mother of F Pass
F is the granddaughter of E. #EPICFAIL
  • Red light. STOP. Checklist item #4 is giving “Fail”
  • Haha see? I had made a stupid mistake in the table (intentionally).
  • F is granddaughter of “E” but I had mistakenly put “F” in the “Male” column.
  • In the actual exam, under the stress, many people make such silly-mistakes.
  • They calculate the sum correctly in their head but on the paper, their hand writes a different thing altogether.
  • Ofcourse in the actual exam, there is time-limit, so you can’t do cross verification/checklist in each and every aptitude question.
  • But in the ‘arrangement’ questions- each dataset comes with 4-5 questions. So, even one silly-mistake will cost you four times the negative marks. Therefore it’s always a good idea to run checklist on arrangement questions.
  • Our final “correct” table looks like this
Generation Male Female Not sure(M/F)
1 Oldest E D
2 Mid aged B C
3 Youngest F A

If you want to construct a family tree, it’ll look like following

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