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10 box parts, 9 boxes of qualified, each weighing 10 grams, a box out of defective, each part weighs

6 Huige2010-04-05 23:11:43 +0000 #1
there is a fraction, the denominator will increase its 2 get 9 points of 7, if the denominator plus 3, get three quarters, the original of this score is the number of
yueryuer12182010-04-05 23:21:22 +0000 #2
1, the first box out a second box out two, and so on tenth out of 10 boxes of 45

to the said parts together, and 45 * 10 = 450 bare, is the first of several box is defective

2, set the score for the x / y

x / (y +2) = 7 / 9

9x = 7y +14

9x-7y = 14 ... (1)

x / (y +3) = 3 / 4

4x = 3y +9

4x-3y = 9. .. (2)

(1) - (2) * 9 / 4
-7y +27 / 4y = 14-81/4
-28y-27y = 56-81

y = 25

x = (9 +25 * 3) / 4 = 21

Score is 21/25

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