Task# Above and below sea level

Illustrative MathematicsVaries

The purpose of this task is to help students interpret signed numbers in a context as a magnitude and a direction and to make sense of the absolute value of a signed number as its magnitude. The questions about the elevation of New Orleans are fairly natural: it is a standard convention to use positive numbers to represent elevations above sea level and negative numbers below sea level. However, it is possible to represent them the other way around. The questions about Denver, while they may seem unnatural, are there to see if students understand that in this kind of context, positive numbers are chosen to represent distances in an arbitrary direction relative to an arbitrary elevation, and that once the reference elevation and positive direction are chosen, the negative values can also be interpreted in the context.