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what fraction of c (Discussion)

sanju09 saidWed, 01 Apr 2009 11:54:39 -0000 ( Link )

a, b, and c are integers and a < b < c. S is the set of all integers from a to b, inclusive. Q is the set of all integers from b to c, inclusive. The median of set S is ¾ b. The median of set Q is 7/8 c. If R is the set of all integers from a to c, inclusive, what fraction of c is the median of set R?

A. 3/8

B. ½

C. 11/16

D. 5/7

E. ¾

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  1. rneve saidWed, 01 Apr 2009 12:19:54 -0000 ( Link )

    ANS :=> C. 11/16

    Prepare the equations like 1) For set S (b-a)/2 = (3/4)b i.e. a = -1/2 b 2) For set Q ( c-b ) / 2 = (7/8) c i.e. b = -6/8 c

    Now for set R , c-a/2 = ? put value of a in the form of b , then put value of b in the form of c , Solve it ( ans : 11/16 c )

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  2. oLahav saidWed, 01 Apr 2009 12:53:22 -0000 ( Link )

    I have a small concern with this question- a median of a set of all integers in an interval can’t be 3/4. If you’re talking about midpoint and real numbers or rational numbers, then this would make more sense. And in that case I would agree with rneve above me, looking at the midpoint of sets S and Q as (b – a)/2 = 3b/4 etc. should work.

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  3. rneve saidThu, 02 Apr 2009 05:02:45 -0000 ( Link )

    Here’s one approach: Set S: We know that the largest number is b and the median is 3b/4. Since the median is in the middle of the numbers of set S, we know that the smallest number in set S is 2b/4 You can see that 3b/4 (the median) lies directly in the middle 2b/4 and b (i.e., 2b/4, 3b/4, 4b/4) So, set S ranges from b/2 to b

    Set Q: Here the largest number is c and the median is 7c/8. Using similar logic from above, we can conclude that set Q ranges from 6c/8 to 8c/8, with 7c/8 squarely in the middle.

    Here’s the important step. 6c/8 is the smallest number in set Q. This value is equivalent to b (the largest value in set S)

    So, now we have a relationship between c and b. We know that 6c/8 = b From here, we can find two integer values for b and c that satisfy this equation amd determine how sets S and Q might look.

    One solution is b=6 and c=8 For set S, we know that the largest value is 6, so keep adding numbers until we meet the criterion that the median is 3/4 b. We do the same with set S, beginning with c=8. From here we can conclude that set S={3,4,5,6} and set Q={6,7,8} The median of {3,4,5,6,7,8} is 5.5, which means the median is 11/16 of c

    We could have chosen other numbers for b and c but the fraction remains 11/16 For example, b=12 and c=16 gives us S={6,7,8,9,10,11,12} and Q={12,13,14,15,16} The median of {6, 7, . . . 15, 16} is 11, making it 11/16 of c

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  4. Sureshbala saidFri, 03 Apr 2009 02:44:45 -0000 ( Link )

    This question can be answered quickly by supposing numbers.

    Given that median of set S = 3/4b and median of Q = 7/8c

    In choosing number try to choose comfortable numbers.

    If we assume c = 8, the median of Q will be 7,

    So set Q = {6,7,8} thus making b =6. But we want b to be divisible by 4 since median of S = 3/4b

    So assume c= 16, then median of Q will be 14.

    So set Q = {12,13,14,15,16}

    Hence b = 12

    Now median of S = 3/4b = 9.

    So set S = {6,7,8,9,10,11,12}

    Hence the R ={6,7,8,9,10,11,12,13,14,15,16}

    So median of R = 11.

    Clearly this is 11/16c

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  5. Sureshbala saidFri, 03 Apr 2009 02:45:32 -0000 ( Link )

    Also, rneve has given a very good explanation for this question. Keep them coming dude….

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