# TIME & SPACE

Time T1
Addition can be reversed by moving numbers to the other side reversing their signs:
x*3 + 2 = 14 is reversed to x = (14 – 2)/3.
This enables us to do both forward and backward calculations.
We also consider the classical quantitative literature consisting of word-problems from especially economy and physics.

Time T2
A stack can change in time by adding a constant number or a constant percentage. Or by adding a variable predictable number.

Space S1
The plane properties of stacks as area and diagonals can be predicted by the 3 Greek Pythagoras’, mini, midi & maxi; and by the 3 Arabic recount-equations:
sinA=a/c, cosA=b/c and tanA=a/b.
Then we look at how to describe spatial properties of solids such as surface and volume by formulas and by a 2-dimensional representation of 3-dimensional shapes.

Space S2
We look at how to calculate the position of points and lines by using a coordinate-system: If Po(x,y) = (3,4) and if ∆y/∆x = (y-4)/(x-3) = 2, then P1(8,y) = (8,2*(8-3)+4) = (8,14). Then we look at how to use the new calculation technology such as computers to calculate a set of numbers, vectors, and a set of vectors, matrices.