PCAT Quantitative Reasoning – Probability of Green Eyes or Red Hair
- Apr 19, 2018
- PCAT Question of the Day
If one in 40 people has green eyes and one in 50 people has red hair, how many people in a city of 230,000 have red hair or green eyes if 320 people in the city have both red hair and green eyes?
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A is correct. First, let’s determine how many people in this city have green eyes and how many have red hair:
Keep in mind that 320 of those with green eyes also have red hair, and 320 of those with red hair also have green eyes. You can think of a Venn diagram where 320 people fall in the area where these two groups overlap. Let’s subtract those to identify those who have only green eyes or red hair:
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