Start from zero — the basic math you need before everything else
Slope measures how steep a line is, meaning how much it climbs for each step you take across. The formula is rise over run: slope = rise ÷ run, where rise is the up-or-down change and run is the across change.
The sign tells you the direction. A line going up to the right has positive slope; going down to the right is negative; a flat line has slope 0. The bigger the size of the slope, the steeper the line. Between two points, rise is the difference in the y-values and run is the difference in the x-values.
Slope is the steepness you feel on a ramp or hill. A wheelchair ramp that rises 1 metre over 12 metres of length has a gentle slope of 1 ÷ 12. Stairs are steeper: up 18 cm over a 30 cm tread. Road signs show it as a percentage — a '10%' hill rises 10 m for every 100 m forward.
▶ Slope