Alright, so we know that due to advanced technology of ski boots, there has been a dramatic drop in the incidence of injuries that occur on the slopes, from 9 injuries per 1,000 skiers in 1950 to 3 injuries per 1,000 skiers in 1980. This has increased the percent of all remaining (i.e. non-slope related) ski related injuries from 10% in 1950 to 25% in 1980.
Alright so let's say there were 100 total ski related injuries in 1950. We know that in 1950, 10% of all ski related injuries did not occur on the slopes. So in 1950, 10 injuries did not occur on the slopes, meaning 90 did. The number of non-slope ski injuries rose to 25% in 1980. So let's say again there were still 100 injuries, therefore, the number totaled 25 in 1980; meaning 75 were slope related injuries.
Our correct answer will be 100% supported by the passage, meaning that it has to be true.
(A) is incorrect because we have not been given any information supporting a constant inverse correlation between slope related injuries and non-slope related injuries. All we know is that from the years of 1950 to 1980 slope related injuries have decreased due to ski boot technology advancement and, as a result, the proportion of non-slope related injuries have increased. However, we have no idea what will continue to happen in the future.
(B) is incorrect because we do not know anything about the drinking habits of those who skied between 1950 and 1980. Though the incidence of non-slope related injuries increases with the amount of alcohol consumed per skier, that does not necessarily mean that alcohol is the reason the percentage of these injuries increased (note that an increased percentage of non-slope related injuries doesn't necessarily mean there have been more non-slope related injuries because this increase is entirely consistent with have a lower total number of ski related injuries).
(C) is incorrect because the technology of ski boots did not affect the INCIDENCE of each type of ski related injury. The technology of ski boots affected the incidence of slope related ski injuries, but nothing in the passage indicates that this technology had any impact on the incidence of non-slope related ski injuries.
(D) is incorrect because we have no evidence supporting this. This could be true, but it doesn't have to be true. It's possible that ski boot technology has reached its zenith in affecting ski related injuries so any new advancements will not affect them.
(E) is CORRECT because as you can see from the makeshift numbers we placed in, from the percentages given us, in 1980, we have a 25:75 ratio of non-slope related injuries to slope related. Meaning that 75% of all ski injuries were slope related. In 1950, we had a 10:90 ratio. Meaning that 90% of all ski related injuries were slope related. Therefore, the injuries that occurred on the slopes of ski resorts made up a smaller percentage of ski related injuries in 1980 than in 1950. This is 100% supported by the passage.
I hope that was helpful. Let me know if you have any other questions!
