Which is the correct formula to convert Fahrenheit to Celsius?

• A. C = (F − 32) × 5/9
• B. C = (F + 32) × 9/5
• C. C = F × 9/5
• D. C = F − 32

Answer: (A)

To convert Fahrenheit to Celsius, you must remove the offset between the scales and then scale the units. The freezing point of water is 32°F, which corresponds to 0°C, so you first subtract 32 from the Fahrenheit value and then multiply by 5/9 to adjust the size of the degree. The correct formula is C = (F − 32) × 5/9.

Example: at boiling point, F is 212. (212 − 32) × 5/9 = 180 × 5/9 = 100, so 212°F equals 100°C.

Why this works: subtracting 32 accounts for the offset between the two scales, and multiplying by 5/9 converts the Fahrenheit degree size to Celsius. Using the other forms would either skip the offset, apply the wrong scale factor, or both, leading to incorrect results.