CA Foundation · Quantitative Aptitude

Blood Relations: formula sheet

Key formulas

Code key is given, not fixed: Meaning of each symbol = as stated in the question; Example only: A + B = A is father of B; A − B = A is mother of B; A × B = A is brother of B; A ÷ B = A is sister of B. Do not assume these in another question.
Reading direction: A ∗ B ∗ C is read as (A to B), then (B to C), then A to C; The first symbol links the first two letters. The second symbol links the second and third letters. The answer is the relation of the first letter to the last.
Gender carried by the first letter: "A is the brother/father of B" ⇒ A is male; "A is the sister/mother of B" ⇒ A is female; The code tells you the gender of the first person only. The second person's gender is known only if another link says it.
Sibling of a parent: Brother of father or mother = uncle; Sister of father or mother = aunt; Father's side is paternal; mother's side is maternal. Use the parent's link in the chain to decide which.
Parent of a parent: Father of father or mother = grandfather; Mother of father or mother = grandmother; Two parent links in a row mean grandparent. The gender of the first person decides grandfather or grandmother.

Draw a family tree for every question that has more than two statements.
Use □ for male, ○ for female, = for spouses, a horizontal line for siblings and a vertical line for parent to child.
Paternal means father's side. Maternal means mother's side.
Father's or mother's brother is an uncle. Father's or mother's sister is an aunt.
A sibling's son is a nephew and a sibling's daughter is a niece, from the viewpoint of the uncle or aunt.
Cousin does not tell you gender. Neither do child, sibling, parent's sibling's child or spouse's sibling.
Spouse's father and mother are in-laws. Your sibling's spouse and your spouse's sibling are also in-law relations.
In coded questions, write the key for each symbol before reading the statement.
Read the question as 'X is what to Y', and make sure you answer from the correct person's viewpoint.
If the options include 'cannot be determined', check whether a gender or link is really missing.
Skip a question if the chain is unclear after one careful attempt. A wrong answer loses 0.25 marks.

Using the code meanings from a previous question. Fix: Write the key afresh for each question before reading the expression.
Reading the chain in the wrong direction. Fix: The answer is always the relation of the first letter to the last letter. Link letters in the order written.

Write the key in short form first. Most lost marks in this topic come from using the wrong symbol meaning.
Two kinds of questions appear: find the relation from an expression, or find the expression for a given relation. For the second kind, test options one by one and drop wrong ones early.
Watch the first letter's gender. If an option makes the first person female when the answer needs a male, eliminate it at once.
Avoid guessing when you cannot decide between two options. A wrong answer costs 0.25 marks, so skip and return if time remains.
Practise a few chains with every symbol swapped around, because exam keys often change which symbol means which relation.