Coded Blood Relations

• How family relations are hidden behind symbols (+, -, x, %) in olympiad-style questions.
• A reliable method: decode each symbol into a plain relation word first, then draw the family tree as usual.
• Why reading the legend carefully (which symbol means what) is the most important first step.

1. Learn the legend first — every coded question gives you a key, e.g. "A + B means A is the father of B".
2. Decode symbol by symbol — convert the whole coded string into plain sentences before analysing.
3. Then apply the Direct Relations method — draw the tree and count generations.
4. Different questions may use different legends — never assume the same symbol always means the same thing across questions.

Legend: A + B means A is the father of B; A - B means A is the mother of B. Given: "P + Q, Q - R". How is P related to R?

Step 1 — decode: P + Q → P is the father of Q. Q - R → Q is the mother of R.
Step 2 — draw: P -> Q -> R (P is Q's father, Q is R's mother)
Step 3 — P is two generations above R, and P is male
Answer: P is R's grandfather.

• Applying a symbol meaning from a previous question to a new question with a different legend.
• Decoding the statement in the wrong order (mixing up who is the parent and who is the child).
• Skipping the decoding step and trying to guess the answer directly from the symbols.

• If A x B means "A is the brother of B", and A x B, B - C are given, how is A related to C?
• Decode: "M + N, N + O" using the legend "+ means father of".
• Why is it important to check the legend every time, even if the symbols look familiar?

Open the Practice tab for graded questions on Coded Blood Relations.