Final answer:
When moving westward by 90 degrees from Nairobi at 6:00 p.m., the time difference is 6 hours earlier, making it 12:00 p.m. (noon) at the destination, which is not listed among the options given in the question.
Step-by-step explanation:
If it is 6:00 p.m. in Nairobi, which is located at 45°E, and we need to find the time at a town 45° West of Nairobi, we must take into account that the Earth is divided into 24 time zones, with each zone covering 15 degrees of longitude. This means that for every 15 degrees we move to the west, we subtract one hour from the current time, and for every 15 degrees we move to the east, we add one hour. Since Nairobi is at 45°E and we are looking at a town 45° West of Nairobi, this represents a 90° difference in longitude.
90° divided by 15° per hour is equal to 6 hours. Because we are moving westward, we subtract these 6 hours from Nairobi's time. So, if it is 6:00 p.m. in Nairobi, it would be 12:00 p.m. (noon) at a town 45° West of Nairobi. The correct answer is b. 12:00 p.m., which is not listed among the options provided, suggesting a typo or error in the question.