数学题再一次英语竞赛中共有20道
答案: 16。
Let x be the number of right answers, y be the numbers of wrong answers, and z be the number of questions not answered。 Then
x + y + z = 20,
5x - 2y = 72。
From the two equations,
7x + 2z = 112。 That is,
7x <= 112, and
x <= 16。
答案: 16。
Let x be the number of right answers, y be the numbers of wrong answers, and z be the number of questions not answered。
Then
x + y + z = 20,
5x - 2y = 72。
From the two equations,
7x + 2z = 112。 That is,
7x <= 112, and
x <= 16。
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