 Now that we have figured out that our 208 on the water heater must be Fahrenheit, let's ask ourselves how much is this in Celsius? Now, we could simply look up the formula, but let's say you forgot to put the formula on your cheat sheet Or you simply blank out during your test. How can we find it if by any chance we still have this data here? I actually can use this data here. We're going to use the advantage that both scales are defined over the properties of water, the boiling and the freezing point. What's the difference here between boiling and freezing? The difference is 100 degrees Celsius. What is the difference here between boiling and freezing? It's 180 degrees Fahrenheit. So a difference of 100 degrees Celsius must be equal to a difference in 180 Fahrenheit. Now the only problem is the two scales do not both start at zero. Fahrenheit starts at 32. So what we have to do, we have to offset it by 32. So we do Celsius is Fahrenheit minus 32. Then we make it equal to 180 Fahrenheit and we multiply it by 100 to get into Celsius. And this, if you look it up, is exactly the formula for converting from Fahrenheit into Celsius. So first we subtract 32 to move the scale down to zero. Then we divide it by 180 Fahrenheit and we multiply by 100 Celsius for the same range of temperatures. So in our case minus 32. So 208 minus 32 times 100 over 180 gives me is 97.7 degrees Celsius. If we look at our significant figures, we had three to start. This conversion is actually definitions. I'm going to keep three significant figures. So 97.7 degrees Celsius is the set point of that water heater, which is actually pretty hot. We're just three degrees below boiling. She's also seen here with Fahrenheit. We were pretty close.