#$&* course MTH 151 Time of submission - 5:44 PM 12 January 2012 Question: `q001. Let A stand for the collection of all whole numbers which have at least one even digit (e.g., 237, 864, 6, 3972 are in the collection, while 397, 135, 1, 9937 are not). Let A ' stand for the collection of all whole numbers which are not in the collection A. Let B stand for the collection { 3, 8, 35, 89, 104, 357, 4321 }. What numbers do B and A have in common?
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Given Solution: Of the numbers in B, 8, 89, 104, 4321 each have at least one even digit and so are common to both sets. Of the numbers in B, 3 is odd, both of the digits in the number 35 are odd, as are all three digits in the number 357. All three of these numbers are therefore in A ' . STUDENT QUESTION In the second part of the question you said BOTH of these numbers are therefore in A’, so does that mean that 3 is not and if so then why not? Also what does the ‘ (is it an apostrophe?) in A’ stand for or is in just a means of separation? INSTRUCTOR RESPONSE Of the numbers in B, the number 3 is in A ', the number 35 is in A ' and the number 357 is in A ' . The apostrophe (you identified it correctly) indicates that you are looking for elements that are NOT in the set. This is in relation to the statement in the problem: Let A ' stand for the collection of all whole numbers which are not in the collection A. &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& Self-critique (if necessary): OK ------------------------------------------------ Self-critique Rating: OK ********************************************* Question: `q002. I have in a room 8 people with dark hair brown, 2 people with bright red hair, and 9 people with light brown or blonde hair. Nobody has more than one hair color. Is it possible that there are exactly 17 people in the room?
YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY Your solution: - If it is already given that there are 8 people with dark brown hair, 2 with light red hair, and 9 with light brown hair, it is generally expected that when one adds the aforementioned numbers together, 19 people are in the room total. Nobody having more than one hair color seems to be irrelevant. Therefore, it would be false to say that there are exactly 17 people in the room. confidence rating #$&*: ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Given Solution: `aIf we assume that dark brown, light brown or blonde, and bright red hair are mutually exclusive (i.e., someone can't be both one category and another, much less all three), then we have at least 8 + 2 + 9 = 19 people in the room, and it is not possible that we have exactly 17. &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& Self-critique (if necessary): Gave way too much focus and thought into the question. Began to question one’s original thought process when presented with the number 17 being against what one originally thought. Otherwise, one was correct in stating one’s answer. ------------------------------------------------ Self-critique Rating: 3 ********************************************* Question: `q003. I have in a room 6 people with dark hair and 10 people with blue eyes. There are only 14 people in the room. But 10 + 6 = 16, which is more than 14. How can this be?
YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY Your solution: - If there are 6 dark headed people, 10 people with blue eyes and a total of 14 people in the room, one would theorize that just because someone would have dark hair would not necessarily mean that they also have blue eyes. confidence rating #$&*: ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Given Solution: `aThe key here is that there is nothing mutully exclusive about these categories-a person can have blue eyes as well as dark hair. So if there are 2 people in the room who have dark hair and blue eyes, which is certainly possible, then when we add 10 + 6 = 16 those two people would be counted twice, once among the 6 blue-eyed people and once among the 10 dark-haired people. So the 16 we get would be 2 too high. To get the correct number we would have to subtract the 2 people who were counted twice to get 16 - 2 = 14 people. &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& Self-critique (if necessary): ------------------------------------------------ Self-critique Rating: 2 ********************************************* Question: `q004. In a set of 100 child's blocks 60 blocks are cubical and 40 blocks are cylindrical. 30 of the blocks are red and 20 of the red blocks are cubical. How many of the cylindrical blocks are red?
YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY Your solution: - 60 blocks being cubical has no bearing on the amount of cylindrical blocks being red, so those numbers are ignored. However, 40 blocks gives one the total amount of cylindrical blocks gives one a number to work with when paired with the fact that 30 blocks are red, and 20 of those 30 blocks are cubical. Therefore, only 10 cylindrical blocks are red. confidence rating #$&*: ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Given Solution: `aOf the 30 red blocks 20 are cubical, so the rest must be cylindrical. This leaves 10 red cylindrical blocks. &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& Self-critique (if necessary): OK ------------------------------------------------ Self-critique Rating: OK " Self-critique (if necessary): ------------------------------------------------ Self-critique rating: " Self-critique (if necessary): ------------------------------------------------ Self-critique rating: #*&!