Zack has a Fahrenheit thermometer which shows a temperature of 29ºF. He says his temperature is above freezing. Jack has a Celsius thermometer. He disagrees and says that the temperature is below zero on his thermometer. Who is right and what is the temperature in degrees Celsius?

SOLUTION

To convert Fahrenheit to Celsius, we first subtract 32. That gives us -3.

Then we multiply by 5/9 to convert to Celsius. When we do this, 3 goes into the denominator and we get -3/9 which is -1/3. Finally we multiply this fraction by 5: 5×-1/3=-5/3=-1.67°C or -1⅔°C.

So Jack was right. The negative value means the temperature is below zero, that is, below freezing. The temperature is 1⅔°C below zero.