The distance on Earth between two consecutive degrees of latitude is approximately how much?

Introduction / Context:
Basic facts about the geometry of the Earth such as distances between lines of latitude and longitude are fundamental to physical geography and map based questions. The Earth is approximately spherical in shape, and degrees of latitude measure north south position. This question asks for the approximate distance between two consecutive degrees of latitude, which is a constant value that does not vary significantly from the equator to the poles.

Given Data / Assumptions:

• The question refers to two consecutive degrees of latitude, that is, a difference of one degree in latitude.
• The options are given in both miles and kilometres, with values around 111 and 121.
• We assume the Earth is approximately a sphere with an average circumference that is commonly used in school level geography.

Concept / Approach:
Latitude lines are parallel circles drawn from east to west on a globe. The total distance around the Earth along a meridian from the equator to the pole is about one quarter of the Earth's circumference. The Earth's mean circumference is roughly 40,075 km, so one quarter is about 10,000 km. There are 90 degrees of latitude from the equator to the pole, so the distance per degree is approximately 10,000 km divided by 90, which is near 111 km. Because the Earth is not a perfect sphere but an oblate spheroid, the precise value changes slightly, but 111 km is the standard approximation used in exams.

Step-by-Step Solution:
Step 1: Recall that the Earth's mean circumference is about 40,075 km. Step 2: The distance from equator to pole is about one quarter of the circumference, roughly 40,075 / 4 ≈ 10,000 km. Step 3: There are 90 degrees of latitude between the equator and the pole, so divide 10,000 km by 90 to find distance per degree. Step 4: 10,000 / 90 is about 111.11 km per degree, so we use the approximate figure 111 km. Step 5: Compare with the multiple choice options and select the one closest to 111 km, which is 111 km itself.

Verification / Alternative check:
Another way to verify is to remember a standard rule of thumb taught in navigation and geography: one degree of latitude is approximately equal to 69 statute miles. Converting 69 miles to kilometres using 1 mile ≈ 1.609 km gives 69 × 1.609 ≈ 111 km. This independent check again confirms that 111 km is the correct approximate distance per degree of latitude.

Why Other Options Are Wrong:

• Approximately 111 miles: This value is closer to 179 km and does not match the known approximate distance per degree in kilometres.
• Approximately 121 miles: This is still not the standard value and would correspond to an even larger distance in kilometres.
• Approximately 121 km: This is higher than the accepted approximation and not typically used in textbooks.
• Approximately 90 km: This underestimates the distance and contradicts the standard figure of around 111 km.

Common Pitfalls:
Students sometimes confuse miles and kilometres and may select 111 miles instead of 111 km. Others may remember a rounded value incorrectly as 100 km. It is important to memorize that one degree of latitude is about 69 miles or 111 km. Understanding how this value arises from the Earth's circumference helps fix it more firmly in memory and reduces guessing errors in the exam.

Final Answer:
The distance between two consecutive degrees of latitude is approximately 111 km.