Number sense should develop early, and what simpler way to do it then to start with elevators?

Why elevators you ask? Well, I just returned from 2 weeks in Italy. Partly for work: training elementary math teachers in Vicenza, Italy on College & Career Ready Standards for UT Dana Center International Fellows and Department of Defense Education Activities; and partly for leisure: touring Venice, Cinque Terre, Florence, Tuscany and Rome with my husband, sister, and brother-in-law. The first thing I noticed was the elevators have negative numbers to indicate those floors below ground zero (i.e. what we usually call floor 1 or Lobby in the U.S.) It’s not the first time I’ve noticed this – in England, in Paris, in Germany – all these other countries indicate on their elevators the ground floor to be 0, the floors above ground 0 are 1, 2, 3…. and the floors below ground zero are -1, -2, -3….

This way of numbering elevators makes sense. Much more sense than Floor 1, or Lobby and then Basement, Basement2 (or LL1, LL2) – which is our typical way of indicating the ground floor (1) and the floors below ground level (Basements/Lower Levels). If you were a young child living in these countries and taking the lifts (or elevators), you are regularly exposed to integer numbers – with a contextual connection that the ground floor of a building is ground 0, and the floors below the ground are negative numbers, and the floors above the ground are positive numbers. It may not even be explicitly explained to young children, though they would be using the terms ‘negative 1’ or ‘negative 2’ to go down below the ground floor. They will have this repeated exposure so when they are ‘officially’ taught about negative numbers in school, they have an immediate connection to prior knowledge about the numbers in an lift/elevator and can make a real-world connection. Negative numbers won’t be new or hard to understand because it’s just the numbers in the elevator. Or – the numbers of the temperature, because let’s not forget, these countries also use the Celsius temperature scale, where freezing is 0, and anything above 0 degrees is above freezing and getting warmer (positive) and anything below 0 degrees is getting colder (negative). The further from 0 in either direction, the warmer or colder you are – again, real-world connection and a contextual understanding of integers.

Number sense. Number lines. Integers. Real-world connections. Just from elevators and temperature scales.

This repeated exposure, informal as it may be, is developing an intuitive understanding of numbers and their real-world meaning. And when students are then exposed to number lines and positive and negative numbers more formally, in a school setting, they already get what that means because it is familiar to them. They can apply what they already know to ‘mathematics’. The formalization makes sense, and connections make sense, and understanding is that much deeper. This is different in the U.S., where students often struggle with the idea of ‘negative’ numbers and number lines and the distance from zero because we are teaching them something new. We don’t have a real-world exposure to negative numbers because we use LL or B1 to represent lower than 0, our ground floor is never called 0, it’s 1 or Lobby or G (ground). Our temperature doesn’t have 0 as the freezing mark – it has 32 degrees Farenheit. Think how much easier it would be to connect negative numbers (those numbers smaller than zero) to negative floors or negative temperatures. Freezing makes sense at 0. Negative temperatures are colder than freezing. Positive temperatures are warmer than freezing. 32 degrees – not quite the same one-to-one connection to a number line, is it?

Anyway – my point is that something as simple as changing the numbers on an elevator to integer representations would go a long way in helping young children develop number sense early on so that by the time they get to school, they already have a natural understanding of positive and negative numbers. Early on they would be exposed to the idea of 0 being the ground level, positive numbers mean higher floors or farther away from ground zero, and negative numbers mean lower floors, below the ground, and the further you go below ground, the more negative you get, the farther away from zero you are. Number lines would then be ‘recognizable’ because there’s a contextual connection. (If we could change our temperature scale to Celsius that would be great too, though that one is a lot harder to do).

Relabel elevator buttons to reflect numbers on a number line – a simple change that could go a long way in developing informal number sense in children.