How to Solve: CUET Reasoning – Blood Relations & Family Trees

How to Solve: CUET Reasoning – Blood Relations & Family Trees

Introduction

"Imagine you’re given a family riddle in your CUET exam—‘A is B’s mother, but B is not A’s daughter.’ Can you crack it in 30 seconds? Master blood relations, and you’ll solve these in half the time, leaving more minutes for tougher questions."

What You Need To Know First

1. Basic family terms: Mother, father, son, daughter, sibling, uncle, aunt, niece, nephew, cousin.
2. Gender symbols: ♂ (male), ♀ (female), = (married), — (sibling), | (parent-child).
3. Logical elimination: If a statement says "X is Y’s child," Y cannot be X’s child.

Key Vocabulary

Formulas To Know

(No algebraic formulas—these are "mental shortcuts" for family trees.)

1. Parent-Child Rule
2. If A is B’s parent, then B is A’s child.

3. MEMORISE THIS: Parent → Child is a one-way arrow.

4. Sibling Rule

5. If A and B share the same parent, they are siblings.

6. MEMORISE THIS: Same parents = siblings (brothers/sisters).

7. Spouse Rule

8. If A is married to B, then A’s in-laws are B’s parents/siblings.

9. MEMORISE THIS: Marriage connects two families.

10. Gender-Specific Terms

11. Uncle: Father’s brother (paternal) or mother’s brother (maternal).
12. Aunt: Father’s sister (paternal) or mother’s sister (maternal).
13. MEMORISE THIS: "Paternal" = father’s side, "maternal" = mother’s side.

Step-by-Step Method

Step 1: Identify the Proband

• Find the person pointing to or talking about the family.
• Example: "Rahul says, ‘This girl is my mother’s daughter.’" → Rahul is the proband.

Step 2: Draw a Gender-Neutral Tree

• Use symbols:
• ♂ = male, ♀ = female, = = married, — = siblings, | = parent-child.
• Start with the proband at the bottom (easiest to build upward).

Step 3: Translate Statements into Symbols

• Convert words into arrows/symbols one by one.
• "A is B’s mother" → A ♀ | B.
• "C is D’s brother" → C ♂ — D (same parents).
• "E is F’s wife" → E ♀ = F ♂.

Step 4: Fill in Missing Links

• Use elimination:
• If X is Y’s child, Y cannot be X’s child.
• If A is B’s uncle, A must be B’s parent’s sibling (or spouse of parent’s sibling).

Step 5: Verify with Questions

• Ask: "Does this match all given statements?"
• Example: If the question says "A is B’s aunt", check:
• Is A female? (Yes, aunt is female.)
• Is A B’s parent’s sister? (Yes, or married to parent’s brother.)

Step 6: Answer the Question

• Read the question carefully: "How is X related to Y?"
• Trace the path from X to Y in your tree.
• Write the most specific relationship (e.g., "maternal uncle" > "uncle").

Worked Example Using Steps

Question: "Pointing to a photo, Priya says, ‘This man’s son is my mother’s brother.’ How is the man in the photo related to Priya?"

Step 1: Proband → Priya. Step 2: Draw Tree

Man in photo (♂)
|
Son (♂) — Priya’s mother (♀)
|
Priya (♀)

Step 3: Translate - "Man’s son" → Man’s child (♂). - "My mother’s brother" → Priya’s maternal uncle. - So, Man’s son = Priya’s maternal uncle.

Step 4: Fill Links - Priya’s maternal uncle is her mother’s brother. - Therefore, Man’s son = Priya’s mother’s brother. - This means Man is Priya’s mother’s father (grandfather).

Step 5: Verify - Man (♂) → Son (♂) → Priya’s mother (♀) → Priya (♀). - Son is Priya’s maternal uncle (correct). - Man is Priya’s grandfather (correct).

Step 6: Answer "The man in the photo is Priya’s maternal grandfather."

Worked Examples

Example 1 - Basic

Question: "A is B’s sister. C is A’s mother. How is C related to B?"

Working: 1. Proband: Not specified → assume B. 2. Draw:
C (♀)
|
A (♀) — B (?) 3. "A is B’s sister" → A and B share parents. 4. "C is A’s mother" → C is A’s parent → C is also B’s parent. 5. Answer: "C is B’s mother."

What we did and why: - Used sibling rule (same parents) and parent-child rule. - Eliminated "father" because C is female.

Example 2 - Medium

Question: "P is Q’s daughter. R is Q’s brother. S is R’s father. How is S related to P?"

Working: 1. Proband: P. 2. Draw:
S (?)
|
Q (?) — R (♂)
|
P (♀) 3. "P is Q’s daughter" → Q is P’s parent (gender unknown). 4. "R is Q’s brother" → R and Q share parents. 5. "S is R’s father" → S is R’s parent → S is also Q’s parent. 6. Since P is Q’s daughter, S is P’s grandparent. 7. Answer: "S is P’s grandfather." (S must be male because he’s R’s father.)

What we did and why: - Used parent-child and sibling rules. - Assigned genders based on terms ("father" = male).

Example 3 - Exam Style

Question: "In a family, F is G’s son. H is I’s daughter. J is H’s brother. G is married to I. How is J related to F?"

Working: 1. Proband: F. 2. Draw:
G (?) = I (?)
| |
F (♂) H (♀) — J (♂) 3. "F is G’s son" → G is F’s parent (gender unknown). 4. "G is married to I" → I is F’s other parent. 5. "H is I’s daughter" → H is F’s sister (same parents). 6. "J is H’s brother" → J is also F’s sibling. 7. Answer: "J is F’s brother."

What we did and why: - Built the tree step-by-step. - Used marriage (=) to connect G and I. - Confirmed J’s gender via "brother" (♂).

Common Mistakes

Exam Traps

1-Minute Recap

"Alright, CUET warriors—here’s your 60-second blood relations cheat sheet: 1. Start with the proband—the person talking. Draw them at the bottom. 2. Translate words into symbols: ♂, ♀, =, —, |. No guesses! 3. Build upward: Parents above, siblings beside, spouses connected with "=". 4. Eliminate wrong options: If the question says ‘not a daughter,’ cross out ‘sister’ if it implies female. 5. Double-check genders: ‘Uncle’ = male, ‘aunt’ = female, ‘parent’ = unknown. 6. Practice 3 trees tonight—one basic, one with in-laws, one with ‘not’ statements. You’ve got this!

Final Tip: "In the exam, if stuck, draw the tree—even a messy one. Half the battle is seeing the relationships!