Intersecting birthday windows in February: Sameer remembers his brother's birthday is after the 15th but before the 18th of February (i.e., 16th or 17th). His sister Kanika remembers it is after the 16th but before the 19th (i.e., 17th or 18th). On which date in February is the birthday?

Introduction / Context:
We combine two strict ranges to isolate a single calendar date. This trains careful parsing of “after/before” phrasing (strict inequalities) versus “on or after/on or before” (inclusive inequalities).

Given Data / Assumptions:

• Sameer: after 15th and before 18th ⇒ {16, 17}.
• Kanika: after 16th and before 19th ⇒ {17, 18}.
• All dates refer to the same February.

Concept / Approach:
Translate each memory into a set; take the intersection. Strict “after/before” excludes endpoints.

Step-by-Step Solution:

Verification / Alternative check:
If either statement were inclusive at a boundary (e.g., “on or after 15th”), the intersection might increase or shift; here, the strict language narrows to a unique value.

Why Other Options Are Wrong:

• 16th/18th: Each conflicts with one of the two strict windows.
• 15th: Explicitly excluded by “after 15th.”
• none of these: We do have a valid date, 17th.

Common Pitfalls:
Including 15 or 18 due to misreading “after/before” as inclusive. Always list candidates explicitly.

Final Answer:
17th February