How many feet (ft) are contained in 399 km, given that 1 km = 3280.84 ft and 1 mi = 5280 ft (exact).
The Correct Answer and Explanation is:
To convert 399 kilometers (km) to feet (ft), we use the conversion factor:1 km=3280.84 ft1 \text{ km} = 3280.84 \text{ ft}1 km=3280.84 ft399 km×3280.84 ft/km=1309035.16 ft399 \text{ km} \times 3280.84 \text{ ft/km} = 1309035.16 \text{ ft}399 km×3280.84 ft/km=1309035.16 ft
Answer: 399 km = 1,309,035.16 feet
Explanation
Unit conversion is an essential mathematical skill used in science, engineering, and everyday life. In this problem, we’re asked to convert a distance from kilometers (km) to feet (ft). The given conversion factor is:1 km=3280.84 ft1 \text{ km} = 3280.84 \text{ ft}1 km=3280.84 ft
This factor is based on the international agreement that defines 1 kilometer as 1000 meters and 1 meter as approximately 3.28084 feet. Multiplying these values gives:1 km=1000×3.28084=3280.84 ft1 \text{ km} = 1000 \times 3.28084 = 3280.84 \text{ ft}1 km=1000×3.28084=3280.84 ft
To convert 399 km into feet, we multiply:399×3280.84=1,309,035.16 ft399 \times 3280.84 = 1,309,035.16 \text{ ft}399×3280.84=1,309,035.16 ft
This calculation tells us that 399 kilometers is equivalent to just over 1.3 million feet. This makes sense because kilometers and feet measure distance, but a kilometer is a much larger unit. It takes thousands of feet to equal even one kilometer.
It’s also useful to understand how this relates to other units like miles. Since 1 mile equals exactly 5280 feet, we could also convert kilometers to miles first, then to feet. However, since a direct conversion factor from kilometers to feet is already provided (and precise), it’s more efficient to use it directly.
Being able to fluently convert between units is vital for interpreting measurements across different systems (metric and imperial). For example, scientific and international measurements are usually in kilometers or meters, while the U.S. often uses miles and feet.
So, the final result is that 399 km equals 1,309,035.16 feet, showing the large scale of this distance when measured in smaller units like feet.
