Document 1: Notes from a speech to Forest Preserve Board of Directors by Fire Chief
Summers can be particularly devastating for forests here in the western U.S.; in some years, over 3.5 million acres of trees
have been lost to fires. We advise using firebreaks as a fire management technique. A firebreak is a strip where trees have
been removed in a forest so that a fire started on one side of the strip will not spread to the other side. Having many
firebreaks helps confine a fire to a small area.
Our forest is roughly in the shape of a 50 kilometer by 50 kilometer square. Each firebreak will be a rectangular strip of land
parallel to one side of the forest, with dimensions 50 kilometers by 0.1 kilometers. Intersecting lines of firebreaks separate
the forest into freestanding smaller sections (called stands), in which any forest fire would be unlikely to spread to the other
Document 2: Diagram of Firebreak Proposal by Forest Preserve Board of Directors
The diagram below shows the 50 km by 50 km square forest divided with three north-south and three east-west firebreak lines.
There are a total of six firebreak lines, which create four stands of trees.
Document 3: Memo from Fire Chief to Forest Preserve Board of Directors
It is the opinion of the fire crew that in contrast to your proposal for three intersecting lines of firebreaks, we believe that
five intersecting lines (five north-south and five east-west) will be more effective at fire containment. Our proposal is given
below. It does appear to be more work for our fire crews to create more firebreaks, but we expect less overall loss to the forest
in case of fire, since only one of the 16 stands would presumably be lost, along with the trees removed to make the firebreaks
in the first place. It may cost more in wages up front, but this offers better protection for the trees in the preserve.
Consider each of the following statements. Does the information in the three sources support the inference as stated?
In the Forest Preserve Board’s original proposal, 30 square kilometers of forest would be cleared for firebreaks.
Comparing the two proposals, the amount of forest cut down for the ten firebreaks in the Fire Chief’s proposal is greater than the amount of forest cut down for the six firebreaks in the original Forest Preserve Board’s proposal, but not twice as great.
In case of the occurrence of an actual fire that destroys one stand of trees, the total area of land lost (firebreaks and fire damage) in the Fire Chief’s proposal would be less than 10% of the total land area of the forest.