Idiot\'s Guides Basic Math and Pre-Algebra

Chapter 19: Graphs 263

Either the vertical axis will become so
crowded with numbers that you can’t
read them anymore, or the graph will
become so big that it won’t fit on the
page. What can you do? One strategy is
not to label every division. They’re still
there to help you to count the height of
the bars, but the scale is easier to read.

The other tactic you can use is what’s
called a broken scale. At the bottom
of the vertical axis, you place a pair of
slashes or a zigzag marker to show that
you’re skipping over some numbers, and
then you begin the scale again after the
break. This graph has a broken axis that
picks up at 300.

y

x

600

550

500

450

400

350

300

250

200

150

100

50

0

y

600

550

500

450

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300

0

x

MATH TRAP

When a graph has a broken scale, the relative sizes of the bars can be distorted. If the

scale jumps from zero to 500 in a short break, a bar that represents 700 could look

almost twice the size of a bar that represents 600. Read carefully. Always check for

broken scales and note how much of a jump they’ve taken.