How Many Inches is 21 cm?
The Correct Answer and Explanation is :
To convert centimeters to inches, the formula is:
[
\text{Inches} = \text{Centimeters} \div 2.54
]
So for 21 cm:
[
\text{Inches} = 21 \div 2.54 = 8.2677 \text{ inches}
]
Thus, 21 cm is approximately 8.27 inches.
Detailed Explanation:
The metric system and the imperial system, which are used to measure length, have different units. Centimeters (cm) belong to the metric system, while inches belong to the imperial system.
The metric system is based on powers of 10, making it easier to convert between different units like millimeters (mm), centimeters (cm), and meters (m). One centimeter is equal to 10 millimeters, and one meter is equal to 100 centimeters. The imperial system, however, is based on units that are not as easily divisible by 10, making conversions more complex.
The relationship between centimeters and inches is established by the conversion factor: 1 inch = 2.54 centimeters. This means that when you need to convert a measurement from centimeters to inches, you divide the number of centimeters by 2.54.
This conversion factor is not arbitrary. It was established by international agreement in 1959, when various English-speaking countries standardized their units of measurement. Before that, the length of an inch could vary slightly depending on the country.
To convert 21 cm into inches, simply divide 21 by 2.54. The result is approximately 8.27 inches, which is the exact measurement when rounded to two decimal places.
Understanding this conversion is useful when you are working with measurements in both systems. It is commonly used in fields like construction, design, and science, where both metric and imperial systems are often used depending on the region or country.