Contestants at a baking contest must use between 5 and 8 of 10 possible ingredients.
Quantity A | Quantity B |
The number of ingredients that must be used to get the smallest possible number of different combinations | The number of ingredients that must be used to get the largest possible number of different combinations |
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Solution
You are forming groups where order doesn’t matter, so use the combination formula. If you use 5 ingredients, then there are: \(\frac{10}{5}\frac{9}{4}\frac{8}{3}\frac{7}{2}\frac{6}{1}\)=252 different combinations. If you use 6 ingredients there are \(\frac{10}{6}\frac{9}{5}\frac{8}{4}\frac{7}{3}\frac{6}{2}\frac{5}{1}\)=210 combinations, if you use 7 there are \(\frac{10}{6}\frac{9}{5}\frac{8}{4}\frac{7}{3}\frac{6}{2}\frac{5}{1}\)=120, and if you use 8 there are \(\frac{10}{8}\frac{9}{7}\frac{8}{6}\frac{7}{5}\frac{6}{4}\frac{5}{3}\frac{4}{2}\frac{3}{1}\)=45.Thus, Quantity A is 8, and Quantity B is 5, choice (A).
A four-person leadership committee is to be chosen from a student council that consists of seven juniors and five seniors. Q is the total number of different leadership committees that include three seniors and one junior.
Quantity A | Quantity B |
Q | 75 |
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Solution
Start by finding out how many groups of three seniors can be chosen from the five seniors: \(\frac{5}{3}\frac{4}{2}\frac{3}{1}\)=10. Next, multiply that total by the number of individual juniors with which those groups can be paired (7) to form the full committee: 10 × 7 = 70. Quantity B is greater.
Six students compete in a table tennis tournament. Each student plays each of the other students four times. What is the total number of games played in the tournament?
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Solution
60
When calculating the number of games, order does not matter.There are two students in each game, so two slots:\(\frac{6}{2}\frac{5}{1}\), because order does not matter you will divide by the factoral for 15 combinations.Each student plays 4 games against each of the other students, so 4(15) = 60 games are played.
What is the difference between the number of three-member committees that can be formed from a group of nine members and the total number of ways there are to arrange the members of such a committee?
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Solution
To find the number of different committees. Make your slots and divide by the factoral \(\frac{9}{3}\frac{8}{2}\frac{7}{1}=84\); eliminate choice (B).To find the number of ways to arrange the committee members, just multiply 9 × 8 × 7 = 504, and eliminate partial choice (E).The difference is 504 − 84 = 420, choice (D).
If the current day and time is 9:30 p.m. on Tuesday, what time will it be (to the nearest minute) 100,000 seconds from now?
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Solution
Dividing 100,000 seconds by 3,600 seconds per hour, you get 27 hours plus 7⁄9 hr. Multiplying 7⁄9 hr by 60 minutes per hour, you get 46(2⁄3) minutes.Therefore, to the nearest minute, 100,000 seconds is equal to 27 hours, 47 minutes. After 24 hours, the time will be 9:30 p.m. Wednesday; 3 hours, 47 minutes after that, it will be 1:17 a.m.,Thursday, choice (D).
Geoff is setting up an aquarium and must choose 4 of 6 different
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Solution
First find the number of groups of fish he can select.This is your number of slots: _ _ _ _ _.There are six fish he can choose for the first slot, 5 for the second and so on: 6 5 4 3. Since order doesn’t matter, you need to divide by the factorial of the number of slots:\(\frac{6213}{4321}\). Reduce your number to get 3 × 5 = 15. For plants you have two slots so 3⁄2 × 2⁄1 = 3. 3 × 15 = 45.The answer is choice (D).
190 students go to a school bake sale. 95 buy a chocolate chip cookie, 75 buy a peanut butter cookie, and at least 12 buy both. What is the least number of students who could have bought neither type of cookie?
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Solution
Substitute the given values into the groups equation:Total = Group 1 + Group 2 − Both + Neither. So 190 = 95 + 75 – 12 + N. N = 32. If you pick a number larger than 12 to represent the number of students who buy both cookies, the number that buy neither cookie also increases.The question asks for the least number that bought neither cookie, so the answer is choice (D).
A certain password must contain 3 distinct digits followed by 2 distinct capital letters. Given ten digits and 26 capital letters, how many different passwords are possible?
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Solution
468,000
List the number of possible options for each character in the password.There are 10 possibilities for the first digit, 9 left for the second, and 8 left for the third.There are 26 possibilities for the first letter and 25 for the second.There are 10 × 9 × 8 × 26 × 25 = 468,000 possible passwords.
Graham’s Catering Service currently employs three chefs and offers three different meals. For an upcoming event, the catering service must provide three meals, with each chef cooking one of the meals.
Quantity A | Quantity B |
The number of assignments of chefs to meals if each chef must cook a different meal | The number of assignments of chefs to meals if each chef may cook any of the three meals |
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Solution
Quantity A places a restriction on which meals a chef can cook because each chef must cook a distinct meal. In this case, there would be 3 × 2 × 1 = 6 different assignments. Quantity B does not place a restriction on which meals a chef can cook. In this case, there would be 3 × 3 × 3 = 27 different assignments, choice (B).
Of the 100 eighth-graders at Easton Junior High, 60 students take gym, 40 take a foreign language, and 30 take both gym and a foreign language.
Quantity A | Quantity B |
30 | The number of students taking neither gym nor a foreign language |
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Solution
Substitute the given values into the groups equation:Total = Group 1 + Group 2 − Both + Neither. 100 = 60 + 40 − 30 + N, giving you N = 30, choice (C).