Which formula correctly converts Celsius to Fahrenheit?

• A. (°C × 1.8) + 32 = °F
• B. (°F − 32) ÷ 1.8 = °C
• C. (°C + 32) × 1.8 = °F
• D. (°F − 32) × 1.8 = °C

Answer: (A)

The main idea is how to convert Celsius to Fahrenheit using the relationship between the two scales: multiply by 1.8 (which is 9/5) to account for the size of the degree, and then add 32 to account for the offset where 0°C equals 32°F.

The correct form does exactly that: Fahrenheit equals Celsius times 1.8, plus 32. For example, 0°C becomes 0 × 1.8 + 32 = 32°F, and 100°C becomes 100 × 1.8 + 32 = 212°F, which matches the known boiling point of water.

The other forms either flip the direction (converting Fahrenheit to Celsius), or mix the operations incorrectly. For instance, subtracting 32 and dividing by 1.8 converts Fahrenheit to Celsius, not Celsius to Fahrenheit; adding 32 after a Celsius value is fine, but multiplying after adding would missize the scale; and using the Fahrenheit value in the calculation with the goal of obtaining Celsius is the wrong direction entirely.