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SSC CGL Reasoning · Blood Relations

Coded Statements and Expressions

Coded questions turned round: either test four statements against one decoded chain, or test four chains to find the one that gives a stated relation.

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Why this matters

Thirteen questions in the bank, every one MODERATE: seven from the 2023 shifts and six from 2024. Each asks you to decode four things instead of one, so the saving comes from eliminating options before you decode them all.

Concept 1 of 2: Checking which statement is correct or NOT correct

Here the chain is decoded once and the options are four claims about it. A claim is correct only if the tree makes it certain; one that might be true, because a gender is open, is not correct.

Definition

1. Decode every link and draw the whole tree before reading the options; the options often name the middle people. 2. Mark each person's gender, or leave it open if no link fixes it. 3. Test each option: true (the tree forces it), false (the tree contradicts it) or not certain (it needs an open gender or an unnamed person). 4. 'Which is correct?' wants the one that is surely true. 'Which is NOT correct?' wants the one the tree contradicts. 5. Fast route: find both people of an option on the tree and say the relation aloud; most options fail on the level (a grandchild called a son) before gender is even needed.

Worked example

In a code, 'A @ B' means 'A is the father of B', 'A # B' means 'A is the sister of B' and 'A & B' means 'A is the wife of B'. For 'P & Q @ R # S @ T', which statement is NOT correct? (i) P is the mother of S. (ii) R is T's father's sister. (iii) Q is T's grandfather. (iv) T is R's son.
Practice this conceptself-check · 3 quick reps

The same idea in a real exam question:

SSC CGL · 2024 · Tier I, 11 Sep 2024, Shift 1 · Q6Moderate

Example 1 · Blood Relations · Coded Statements and Expressions

In a certain code language, A + B means ‘A is the son of B’, A − B means ‘A is the wife of B’, A ×\times B means ‘A is the brother of B’ and A ÷\div B means ‘A is the mother of B’. Based on the above, if ‘P + Q ÷\div R − T ×\times M’, which of the following is true?

Treating 'possible' as 'correct'

A statement that holds only if an open gender goes one way is not a correct statement. In a 'which is correct' question, the answer is the one the tree forces.

Checking only the two ends of the chain

Statement options usually name people in the middle of the chain, such as the second and fourth. Draw the whole tree first; decoding only the ends leaves those options untestable.
Drill 7 more on checking which statement is correct or not correct

Concept 2 of 2: Finding the expression that gives a stated relation

Now the relation is given and the four options are coded chains. Instead of decoding all four, turn the relation into a path, note the genders it needs, and throw out every option whose first link already gets them wrong.

Definition

1. Turn the wanted relation into a path from the second person: 'Z is the wife's father's mother of L' is L, then L's wife, then her father, then his mother, Z. 2. Note the genders the path needs. Here Z is a mother, so Z is female. 3. Eliminate by the first link: an option that makes Z a brother, father or husband fails at once. 4. Then check the last link, which must join the path to the second person correctly. 5. Decode in full only the one or two options left.

Worked example

In a code, 'A ~ B' means 'A is the son of B', 'A ! B' means 'A is the wife of B', 'A @ B' means 'A is the father of B' and 'A # B' means 'A is the sister of B'. Which expression means 'P is the father's sister of S'? (i) P # Q @ S (ii) P ! Q @ S (iii) P ~ Q @ S (iv) P # Q ! S
Practice this conceptself-check · 3 quick reps

The same idea in a real exam question:

SSC CGL · 2024 · Tier I, 23 Sep 2024, Shift 3 · Q25Moderate

Example 2 · Blood Relations · Coded Statements and Expressions

In a certain code language, 'A & B' means ‘ A is the brother of B’, 'A x B' means ‘A is the father of B’, 'A ? B' means ‘A is the mother of B’ and 'A ! B' means ‘A is the wife of B’. Which of the following means that W is the mother's mother of P?

Decoding every option in full

Four full decodings cost most of a minute. The gender of the first person and the last link usually remove two or three options; decode only what is left.

Building the path from the wrong end

'Z is the wife's mother of L' starts at L: L's wife, then her mother. Starting at Z and reading 'wife' first gives a path to someone else entirely.
Drill 4 more on finding the expression that gives a stated relation

Summary — formulas & gotchas at a glance

A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.

Watch out for (4)

Test yourself on Blood Relations

20 past SSC CGL questions from this chapter, timed at 12 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.

Take the Blood Relations chapter testDrill all 13 questions