# DBT JRF 2022 — Question 22

Exam: DBT JRF 2022 · Section: A · Topic: Aptitude › Geometry & Circumference · Difficulty: Medium

## Question

An aircraft circumnavigates the earth 10 km above the earth's surface. If it completes one full circle, the distance covered will be _____ greater than the circumference of the earth. (Assume earth radius is 3280 km, and π = 3.14)

## Options

- **A.** 62.8 km
- **B.** 628 km
- **C.** 6280 km
- **D.** 12560 km

## Answer

Option A

## Explanation

Extra circumference when flying 10 km above Earth's surface: Circumference of Earth at surface: $C = 2\pi R$ Circumference at altitude h: $C' = 2\pi(R + h)$ Extra distance covered: $\Delta C = C' - C = 2\pi(R + h) - 2\pi R = 2\pi h$ $\Delta C = 2 \times 3.14 \times 10\,\text{km} = 62.8\,\text{km}$ Key insight: The extra circumference depends ONLY on the altitude (h), not on Earth's radius. Regardless of the actual radius, each additional km of radius adds exactly $2\pi \approx 6.28$ km of circumference. Answer: 62.8 km (Option 1).

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