What is the greatest number on the vertical axis?

Answer 1

There is no greatest value on either axis - they go on forever.

However, when drawing a graph or chart, choose your scale so that each unit is a sensible measure, which depends upon the amount of space you have to draw your graph in and the largest value that needs to be shown, and then mark sensible intervals.

When using graph paper, you should notice that there are big squares, ½ big squares and little squares marked, the bigger squares being marked by thicker lines. The ½ big squares are marked every 5 little squares and the big squares marked every 10 little squares.

To decide the largest value on an axis, count how many big squares long the axis is, multiply by 10 (to get how many little squares there are) and divide this into the largest value you need to display and round the result UP to the next sensible measure. A sensible measure is 1, 2, 5, 10, 0.5, 0.2, 0.1 etc for each little square - the sensible measure is so that it is easy to sub-divide each little square for values that are not exact multiples so that part way along the little squares can be drawn. Each axis is usually labelled at each big square, so the largest value written would depend upon how many big squares there are.

Graph paper is printed at different scales, but a common one is that each little square is 2 mm, each ½ big square is 1 cm and each big square is 2 cm.

Answer 2

There is no greatest value: the axis can go on forever - for example in a graph of y = x^2 or y = 1/x (x>0) or y = tan(x) (-pi/2<x<pi/2).

Answer 3

The greatest number you write on an axis is up to you; but you will normally choose the greatest number according to the data you want to graph.