Final answer:
To convert 21.0 meters to feet, multiply by the conversion factor of 3.28 feet per meter, resulting in 68.88 feet, which is rounded to 68.9 feet to three significant figures.
Step-by-step explanation:
To answer the question, 'how many feet equal 21.0 m?', we start by using the conversion factor that 1 meter equals 3.28 feet. Therefore, we multiply 21.0 meters by 3.28 feet to find the equivalent in feet:
21.0 meters × 3.28 feet/meter = 68.88 feet
To express this value to three significant figures, we round 68.88 feet to 68.9 feet.