right arrow
Examples: Monday, today, last week, Mar 26, 3/26/04
Upcoming changes to the way we log in on College Confidential. Read more here.

Math help center

1246716

Replies to: Math help center

  • esneyesney 109 replies15 threads Junior Member
    Heres a probability question.
    There are 3 Republicans and 2 Democrats on a Senate committee. If a 3 person subcomittee is to be formed from this committee, what is the probability of selecting 2 Republicans and 1 Democrat?
    I know that no. of ways to select 2 Rep. is 3, and that no. of ways to select 1 Dem. is 2 for 6 (3 x 2) possible ways. But how do you determine the total number of ways?(6/?)
    · Reply · Share
  • altamashaltamash 243 replies1 threads Junior Member
    the total is 10 because is 5 C 3. so you get 10 since there are a total of five peopel for 3 spots.
    · Reply · Share
  • NightShadeQueenNightShadeQueen 264 replies4 threads Junior Member
    Where A is not equal to 1, (A^7-A^6)/(A-1)=?
    A)a/(a-1)
    B)1/(a-1)
    C)A^6-A^5
    D) A^5
    E)A^6

    The book says E, and I guessed A. How do you do this one?

    factor out A^6 from numerator: A^6(A-1)/(A-1)

    then divide out (A-1)
    · Reply · Share
  • esneyesney 109 replies15 threads Junior Member
    What is the least interger greater than 999 that is divisible by 6, 8, 9?

    I was able to do this question fairly quickly by trial and error but was wandering if there is perhaps a mathematical and more direct approach. (maybe prime factorization)
    · Reply · Share
  • esneyesney 109 replies15 threads Junior Member
    bump. anyone?
    · Reply · Share
  • goldring2012goldring2012 294 replies17 threads Member
    Id just use trial/error. It works nearly 100% of the time and I don't feel like memorizing random facts and theorems
    · Reply · Share
  • GreyWolfGreyWolf 260 replies21 threads Junior Member
    Use prime factorization. 6 is 2*3, 8 is 2^3, and 9 is 3^2. The find the LCM, just choose the highest power of each factor. This gives you (2^3)*(3^2) = 8*9 = 72. Thus the number must be a multiple of 72. It is simple to see that the first multiple of 72 greater than 999 is 1008.
    · Reply · Share
  • wesurawesura 40 replies1 threads New Member
    difficult set question: a study of 400 fruit orchards showed that 250 of the orchards grew apples, 140 grew pears, 95 grew plums, 70 grew only apples and pears, 30 grew only apples and plums, 45 grew only pears and plums, and 10 grew all three.
    18. how many of the orchards grew only apples or plums?
    a) 30
    b) 130
    c) 150
    d) 180
    e) 345

    19. How many of the orchards grew no apples, pears, or plums?
    a) 0
    b) 80
    c) 165
    d) 235
    e) 320
    · Reply · Share
  • esneyesney 109 replies15 threads Junior Member
    18. the answer is a
    19. I think the answer should be 50 but I dont see it as a choice?

    The easiest way to solve this is to make a venn diagram with three circles. Start with the last piece of information and work your way back while filling in your chart. I'm not sure why I'm not getting an answer choice for q 19. Maybe there is a mistake.
    · Reply · Share
  • altamashaltamash 243 replies1 threads Junior Member
    whre did u get these problems from? is the first one D) 180 and the last one b) 80 .
    · Reply · Share
  • altamashaltamash 243 replies1 threads Junior Member
    whre did u get these problems from? is the first one D) 180 and the last one b) 80 .
    · Reply · Share
  • altamashaltamash 243 replies1 threads Junior Member
    nvr mind i think ezrahusney is right about the last one. i think it is 50 also.
    · Reply · Share
  • altamashaltamash 243 replies1 threads Junior Member
    the first one should be 150 b/c u have to do (250-70-30-10) + (95-45-30)
    apples + plums
    · Reply · Share
  • alwayshope2400alwayshope2400 21 replies24 threads Junior Member
    @ Arachnotron
    this is related to GRE's question about rate and time. I figured out the rates but can you explain why you did this : (27sec/90ft)(100ft) = 30 seconds.?
    · Reply · Share
  • wesurawesura 40 replies1 threads New Member
    guys, the answers are 18. C (150) so altamash got it correct, 19. B (80) i dont understand why though
    · Reply · Share
  • esneyesney 109 replies15 threads Junior Member
    I'm sorry, I misread the question. q 18 is indeed 150.
    19. the answer is b) 80. @altamash why did you switch answers
    · Reply · Share
  • esneyesney 109 replies15 threads Junior Member
    oops I was writing while you posted it.
    Here is my explanation: first make 3 overlapping circles labeled apples, pears, and plums
    fill out the venn diagram as follows
    1. the place where the 3 circles intersect will be 10
    2. the place where only apples and plums intersect will be 30
    3. the place where only pears and plums intersect will be 45
    4. the place where only apples and pears intersect will be 70
    5. remaining apples will be 250-30-10-70=140
    6. remaining pears will be 140-70-10-45=15
    7. remaining plums will be 95-30-10-45=10

    18. only apples or only plums is 140+10=150
    19. to see how many are none use 400-140-30-70-10-15-45-10=80
    · Reply · Share
  • wesurawesura 40 replies1 threads New Member
    thank you so much, that was a really great explanation
    · Reply · Share
  • MarioleeMariolee 143 replies39 threads Junior Member
    In the BB, there is this example question concerning combinations:
    There are 12 students in the school theater class. Two students will be responsible for finding the props needed for the skit the class is performing. How many different pairs of students can be chosen to find the props?

    - To get the answer, you first multiply 12 by 11 to get the number of ways of choosing a pair of students, and then you divide by 2 because each pair of students can be chosen in two different ways. The answer is 66.

    I do not understand why we have to divide by 2 because each pair of students can be chosen in two different ways. I thought in combinations, the order doesn't matter, so we shouldn't have to worry about this. And why are we dividing? I am confused. :(
    · Reply · Share
  • SilverAuroraSilverAurora 167 replies12 threads Junior Member
    You multiply 12 by 11 to find the number of groups of 2 out of 12 people. For the first person, there are 12 possibilities, and for the second person, there are 11 possibilities. (You can't have a person be the first and second choices.) Therefore you must multiply 12 by 11.
    Next, you have to divide by 2. From what I did before, each pair of students can be chosen in two different ways. For example, student A and student B can be chosen as A then B, or B then A. To get rid of these extra pairs, we divide our answer from the first step by 2.
    · Reply · Share
This discussion has been closed.

Recent Activity