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Posted: Fri Aug 31, 2007 11:31 am |
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Hello,
#10: A second grade class is writing reports on birds. The students' teacher has given them a list of 6 birds they can choose to write about. If Lizzie wants to write a report that includes two or three of the birds, how many different reports can she write?
Solution: First find the number of 2-bird reports - YYNNNN, then consider the number of 3-bird reports - YYYNNN, add them together.
HOWEVER, isn't it the case that if you pick one bird, you will have to pick another one? i.e. you wouldn't write 2 reports on the same bird?
Also:
#13: Mario's Pizza has 2 choices of crist: deep dish and thin-and crispy. The restaurant also has a choice of 5 toppings: tomatoes, sausage, peppers, onions and pepperoni. Finally, Mario's offers every pizza in extra-cheese as well as regular. If Linda's volleyball team decides to order a pizza with four toppins, how many different choices do the teammates have at Mario's Pizza?
Solution: Consider the toppings first: YYYYN
HOWEVER, if they picked one topping, wouldn't they not pick it again?
Finally:
#7: A British spy is trying to escape from his prison cell. The lock requires him to enter one number, from 1-9, and then push a pair of colored button simultaneously. He can make one attempt every 3 seconds. If there are 6 colored buttons, what is the longest possible time it could take the spy to escape from the prison cell?
Solution: The different pairs of colored buttons - YYNNNN
HOWEVER, if he had to press the colored buttons simultaneously, then if he pressed one color button, couldn't he not press it again?
Thank you.
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Stacey Koprince
MGMAT STAFF
| Joined: 06 Mar 2007 |
| Posts: 2293 |
Location: San Francisco
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Posted: Sat Sep 01, 2007 4:19 pm |
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Yes to all three. The anagram grid method already factors this in. For example, the grid YYNNNN already says that you pick 2 (different) birds and do not pick the other four birds. The six letters represent the 6 different birds. And so on for the other examples.
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