Which is the correct formula to convert Celsius to Fahrenheit?

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

Answer: (A)

To convert Celsius to Fahrenheit, multiply by 9/5 and then add 32. This two-step operation matches how the scales align: the 9/5 scales the size of the degree from Celsius to Fahrenheit, and adding 32 shifts the zero point from 0°C to 32°F. For example, 0°C becomes 32°F, and 100°C becomes 212°F (100×9/5 + 32 = 212). The other forms mess up either the scaling or the offset: using 5/9 would apply the inverse direction (Fahrenheit to Celsius), subtracting 32 instead of adding changes the point where the scales start, and placing the 32 inside the multiplication also distorts the result. So the correct expression is multiply by 9/5, then add 32.