A is at 50°N and B is at 10°N, If A and B are on the same longitude, find the distance AS. Correct your answer…

Analyze the question: A and B lie on the same longitude (the same meridian), so the distance between them is an arc along a great circle. "AS" is a typo for AB. We need the arc length from latitude 10°N to latitude 50°N.

Concept: On the same longitude, the angle at the Earth's centre equals the difference in latitude (both points are in the same hemisphere). The arc length is

Distance = (θ/360) × 2πR

Solution:

1. Angle subtended at the centre: θ = 50° − 10° = 40°
2. Distance = (40/360) × 2 × π × 6400
3. 2πR = 2 × 3.142 × 6400 ≈ 40212.4 (using π = 22/7 gives 40228.6)
4. Multiply by 1/9: 40212.4 ÷ 9 ≈ 4468.0 (with π = 3.14159, the exact figure is 4468.99 ≈ 4469)

Computing more carefully: 2π × 6400 = 12800π = 40212.386. Dividing by 9 gives 4468.04 km, so to four significant figures the distance is about 4468 km.

With π = 22/7: 12800 × 22/7 = 40228.57, and dividing by 9 gives 4469.8 km, which is about 4470 km.

Comparing with the options: The options are 6468, 5469, 4470, 3470 and 2488. The only value close to our result is C. 4470 km. It matches the π = 22/7 calculation, which is the usual approach in NECO papers. Using π = 3.142 exactly gives about 4468 km, and the examiners' key rounds to 4470 km.

Tip: For two points on the same longitude, subtract their latitudes if they are on the same side of the equator and add them if they are on opposite sides. Then use (θ/360) × 2πR. Always check which value of π the options match (22/7 or 3.142).