Quantitative Aptitude · Blood Relations

Coded Blood Relations for CA Foundation

Updated 1 October 2026 · Fact-checked

Coded blood relations use symbols like +, −, × and ÷ to stand for relations such as father, mother, brother or sister. To solve them, note the code meanings given in the question, convert each symbol into a relation, then chain the relations in order on a small family tree to find the final relationship.

Understand Coded Blood Relations

In a normal blood relation question, the relation is written in words: "A is the father of B." In a coded question, the same fact is written as a symbol: A + B. The question tells you what each symbol means. Your job is to translate the symbols back into words and then solve it like any family-tree problem.

The most important point: the code meanings change from question to question. In one paper + may mean father. In the next, + may mean sister. Never carry a code from one question to another. Always read the key given in the question first.

A chain such as A × B + C is read as a story, left to right. A is related to B by one symbol. B is related to C by the next symbol. You combine the two links to get how A is related to C. Longer chains just add more links.

Each symbol usually carries two facts: the relation (parent, sibling, etc.) and the gender of the first person. For example, "A is the brother of B" tells you A is male. These gender facts often decide the final answer, such as uncle versus aunt. Sometimes a symbol does not give the gender of the second person, so you can only conclude what the facts support.

So the skill has three parts: translate the symbols, draw the links, and name the final relation from the first person to the last.

Key formulas to remember

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.

How to solve Coded Blood Relations questions

This method works for any coded blood relation question, whether it asks for the relation or asks which expression shows a given relation.

1Write the code key from the question in your rough space, one line per symbol, with the gender of the first person.
2Break the given expression into links, one pair of letters at a time, for example A × B and B + C.
3Replace each symbol with its relation in words: A is brother of B, B is father of C.
4Draw a small tree or write short notation such as A(M) – B(M) – C, marking gender where the code gives it.
5Combine the links from the first letter to the last. Two parent links give a grandparent. A sibling link followed by a parent link gives an uncle or aunt.
6Decide the final name using the gender of the first letter and which parent's side it is, paternal or maternal.
7If the question gives an expression in each option, convert every option the same way and match it to the required relation.
8Compare your result with the four options. If none matches, recheck the code key and the order of the links.

Quickest way: Translate and chain, then match the option

When to use it: Use this for every coded blood relation MCQ. It takes under a minute once you practise.

Jot the key in short form, like + = F, − = M, × = B, ÷ = S.
Read the expression left to right and write the relation words under each symbol, like B then F.
Chain them: brother of father means uncle. Mother of mother means maternal grandmother.
For "which expression shows X" questions, test the options and drop any whose first symbol gives the wrong gender or wrong relation.
Skip a question if the key has more than four symbols and the chain is long, and return to it after the easy MCQs. A wrong answer costs 0.25 marks.

Common mistakes in Coded Blood Relations

Using the code meanings from a previous question.
After practising many problems, + starts to feel like it always means father.
Fix: Write the key afresh for each question before reading the expression.
Reading the chain in the wrong direction.
Students read A × B + C as C related to A instead of A related to C.
Fix: The answer is always the relation of the first letter to the last letter. Link letters in the order written.
Ignoring gender given by the code.
The symbol is read only as a relation, so the sex of the first person is missed.
Fix: Mark the gender next to the first letter of each link. It decides uncle versus aunt, and grandfather versus grandmother.
Mixing paternal and maternal sides.
A sibling of a parent is called just "uncle", without checking whose sibling it is.
Fix: Check the parent in the chain. If the parent link is father, the side is paternal. If it is mother, it is maternal.
Assuming the gender of the second person.
A symbol like "sister of" is wrongly taken to mean the second person is also female.
Fix: Take gender only from what the code states about the first person in that link. If the answer depends on an unknown gender, the correct choice may be the neutral relation or "cannot be determined".
Stopping after the first two links in a longer chain.
Students rush and name the relation between the first two letters.
Fix: Count the symbols and make sure each one is used before you write the final relation.

Worked examples

Example 1

In a certain code: A + B means A is the father of B; A − B means A is the mother of B; A × B means A is the brother of B; A ÷ B means A is the sister of B. In the expression P × Q + R, how is P related to R? Options: (a) Father (b) Paternal uncle (c) Maternal uncle (d) Grandfather

Show the solution

Convert the symbols: P × Q means P is the brother of Q. Q + R means Q is the father of R.
So P is male, and P is the brother of Q, who is R's father.
The brother of a person's father is the paternal uncle.
Check the other options: P is not R's father, because Q is. P is not a grandfather, because P is a sibling of R's father, not a parent of R's parent.

Answer: (b) Paternal uncle

Example 2

Using the same code (+ = father of, − = mother of, × = brother of, ÷ = sister of), in the expression M ÷ N − O, how is M related to O? Options: (a) Mother (b) Maternal aunt (c) Paternal aunt (d) Grandmother

Show the solution

M ÷ N means M is the sister of N, so M is female.
N − O means N is the mother of O.
So M is the sister of O's mother.
A mother's sister is the maternal aunt of O.
It is not paternal, because the parent in the chain is the mother.

Answer: (b) Maternal aunt

Example 3

Using the same code (+ = father of, − = mother of, × = brother of, ÷ = sister of), which expression shows that X is the grandfather of Y? Options: (a) X + Z − Y (b) X − Z + Y (c) X × Z + Y (d) X ÷ Z − Y

Show the solution

A grandfather needs two parent links in a row, and the first person must be male.
(a) X + Z means X is the father of Z. Z − Y means Z is the mother of Y. So X is the father of Y's mother, which makes X the maternal grandfather of Y.
(b) X − Z means X is the mother of Z, so X is female. X is a grandmother, not a grandfather.
(c) X × Z + Y means X is the brother of Z, and Z is the father of Y. X is the paternal uncle of Y.
(d) X ÷ Z − Y means X is the sister of Z, and Z is the mother of Y. X is the maternal aunt of Y.

Answer: (a) X + Z − Y

Exam tips

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.

Practice questions from Blood Relations

Coded Blood Relations: frequently asked questions

Do + and × always mean the same thing in coded blood relations?

No. The meaning of each symbol is given in the question and it changes between questions. Always read the key given with the problem and never rely on memory from earlier questions.

How do I read an expression like A × B + C?

Read it left to right as links. A × B links A and B, and B + C links B and C. Convert each into words and combine them to find how A is related to C.

How is this different from normal blood relation questions?

The family logic is the same. The only extra step is decoding symbols into relations first. After that, you solve it with a family tree like any direct blood relation problem.

What if the gender of a person is not clear from the code?

Use only the genders the code actually gives you. If the answer would need an unknown gender, look for an option that does not depend on it, or one that says the relation cannot be determined.