Bunuel wrote:

How many of the regions shown had a population increase of less than 5% between 1940 and 1972?

(A) 0

(B) 1

(C) 2

(D) 3

(E) 4

Stacked column charts are hard. Each vertical bar typically, as here, contains numbers that must be calculated by chopping the bar into segments and subtracting height values to get amounts.

Despite my familiarity with graphs, and despite believing that the answer was "zero," I was not certain. These numbers can be hard to eyeball.

All numbers discussed are in

millions.

So I solved by:

1) finding the population number in 1940

2) calculating what would = 5 percent growth, and

3)

without being exact, seeing whether or not the 1972 figure was greater than my calculated growth figure.

If so, growth was greater than 5 percent.

The numbers as I measured them:

NORTHEAST

1940 = 40. Add 5 percent, = 42. 1972 figure (difference between top and bottom lines of

solid dark gray part) is greater than 42

NORTH CENTRAL

1940 = 30. Add 5 percent = 31.5. 1972 figure (difference between top and bottom lines of

cross-hatched gray part) is greater than 31.5

SOUTH

1940 = 40. Same as Northeast. 1972 figure (difference between top and bottom lines of

light gray part) is greater than 42

WEST

1940 = 20. Add 5 percent = 21. 1972 figure (difference between top and bottom lines of

solid white part) is greater than 21

ANSWER A

Peanut gallery: you do not have to look at the chart.

I have experience with graphs.

In case reading this kind of graph is not familiar, I have attached the way I measured each region.

I would not replicate this detail on test day.

But you do have to be able to ballpark it. These annotations show how to calculate fairly accurate figures.

Finding the numbers on the annotated graph took me about 2.5 minutes. The method I used to answer the question took one minute.

Notice that the top of one region constitutes the bottom of another. Beginning numbers in the same color as previous region indicate as much.

Finally, circled numbers are totals from 1940 and 1972; they are what need to be compared.

To measure growth:

1) find 1940 lower end value, from where the line on the bottom of the segment that corresponds with the region "hits" on the left side of graph (e.g. North Central is hatched crosswise)

2) subtract from 1940 higher end value, found by seeing where the top line from that segment hits on the left side of graph - that is the 1940 population number

3) do the same for 1972 - that is the 1972 population number

4) divide 1972 by 1940 - you will get a 1.xx figure. The .xx is the percentage growth in decimal form

How the numbers fell out as I read them:

NORTHEAST:

1940 = 40

1972 = 50

50/40 = 1.25 = 25 percent growth

NORTH CENTRAL

1940 = 30

1972 = 55

55/30 = 1.83 = 83 percent growth

SOUTH

1940 = 40

1972 = 70

70/40 = 1.75 = 75 percent growth

WEST

1940 = 20

1972 = 30

30/20 = 1.5 = 50 percent growth

None of the regions experienced less than 5 percent growth - Answer A

Attachment:

popchart.png [ 74.39 KiB | Viewed 1217 times ]
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