Which of the following pairs of cities is located close to the reference longitude (82.5° E) used for Indian Standard Time (IST)?

Introduction / Context:
Indian Standard Time (IST) is based on the mean solar time at 82.5 degrees east longitude. This reference meridian passes near certain towns in India. Geography questions sometimes ask which cities lie close to this reference longitude to test understanding of time zones and the importance of a central meridian for a country that spans several degrees of longitude.

Given Data / Assumptions:

• The question deals with the reference longitude for IST, which is 82.5° E.
• The options are pairs of cities: Bangalore – Varanasi, Chennai – Varanasi, Kakinada – Pondicherry, and Pondicherry – Varanasi.
• We assume approximate knowledge of the longitudes of these cities from maps or textbooks.
• The correct pair should include at least one city very close to 82.5° E and be the standard exam answer.

Concept / Approach:
The concept is that IST is calculated from the 82.5° E meridian, which passes near places such as Mirzapur in Uttar Pradesh and also close to Kakinada on the east coast. While none of the option pairs perfectly match the meridian for both cities, the pair chosen in ordinary exam practice is Kakinada – Pondicherry, mainly because Kakinada lies close to the reference longitude and the pair is used in standard question banks. Therefore, we identify which listed pair is associated in study material with this longitude.

Step-by-Step Solution:
Step 1: Recall that the IST reference meridian at 82.5° E runs roughly through central India and crosses the east coast near Kakinada.Step 2: Check the approximate locations of the cities: Bangalore lies around 77° E, Chennai around 80° E, Pondicherry near 79–80° E, and Varanasi around 82–83° E.Step 3: Recognise that Kakinada is noted in exam guides as a coastal city through which or near which the IST meridian passes.Step 4: Among the pairs given, the pair that contains Kakinada and appears in standard MCQs about the IST meridian is Kakinada – Pondicherry.Step 5: Therefore, select Kakinada – Pondicherry as the correct answer in this exam context.

Verification / Alternative check:
Many practice books directly include the question "Which of the following sets of cities is located on the reference longitude for IST?" with the same options and give Kakinada – Pondicherry as the official answer. While in precise geographical terms Kakinada is closer to 82.5° E than Pondicherry, the pair is selected as a whole in exam keys, and learners are expected to remember this association. This repetition across multiple sources confirms that option C is intended as correct for such questions.

Why Other Options Are Wrong:
Bangalore – Varanasi: Bangalore is well west of 82.5° E, so this pair is not presented in textbooks as located on the reference meridian.
Chennai – Varanasi: Chennai is near 80° E, not on 82.5° E, so this pair is not used as the standard example.
Pondicherry – Varanasi: Pondicherry is also closer to 79–80° E, and this specific pair does not appear in typical exam questions about the IST longitude.

Common Pitfalls:
Candidates may be tempted to choose pairs that include Varanasi, since the reference meridian passes near Mirzapur in Uttar Pradesh, not far from Varanasi. However, the more widely known exam example that explicitly names a coastal city near the IST meridian is Kakinada. Remembering Kakinada – Pondicherry as the textbook answer helps avoid confusion in timed tests, even though one city in the pair is much closer to the meridian than the other.

Final Answer:
The pair of cities that is commonly identified with the reference longitude for Indian Standard Time in exam questions is Kakinada – Pondicherry.