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Summer Clouds

21/06/2017 at 08:56
Answers
2
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There are 50 bricks of white, blue and red colour in the box. The number of white bricks is eleven times the number of blue ones. There are fewer red ones than while ones, but more red ones than blue ones. How many fewer red bricks are there than white ones?
A. 2
B. 11
C. 19
D. 22




    List of answers
  • ...
    Phan Thanh Tinh Coordinator 21/06/2017 at 11:25

    Let b,r,w be the number of blue bricks,red ones and white ones

    \(\left(b,r,w\in Z^+;b+r+w=50;b< r< w;w=11b\right)\).We have :

    \(\circledast b+r+w=50\Rightarrow b+w< 50\)

    \(\circledast w>r\Rightarrow b+w>r\Rightarrow2\left(b+w\right)>r+b+w\Rightarrow b+w>25\)

    \(\Rightarrow25< 12b< 50\Rightarrow2< b\le4\)

    If b = 3,then w = 33 and r = 50 - 3 - 33 = 14 (satisfy)

    If b = 4,then w = 44 and r = 50 - 4 - 44 = 2 (absurd)

    Hence,(b,r,w) = (3 ; 14 ; 33) and w - r = 19

    So,the answer is C

  • ...
    Lê Quốc Trần Anh Coordinator 21/06/2017 at 09:05

    The answer is C: 19

    There are: 33 bricks of white, 3 bricks of blue (33:11=3), 14 bricks of red (50-33-3=14)

    There are: 33-14=19 fewer red bricks than white ones.


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