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【OG20-P165-122题】
Mark and Ann together were allocated n boxes of cookies to sell for a club project Mark sold 10 boxes less than n and Ann sold 2 boxes less than n. If Mark and Ann have each sold at least one box of cookies, but together they have sold less than n boxes, what is the value of n ?
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【答案】A
【解析】根据已知条件,Mark卖了n-10盒,Ann卖了n-2盒。
其中:n-10≥1,n-2≥1,且有(n-10)+(n-2)<n,,从而解得11≤n<12,所以n=11.
【知识补充】
加法单调性:如果x>y,z是任意实数或者整式,那么x+z>y+z。
乘法原则:如果x>y,z>0,那么xz>yz;如果x>y,z<0,那么xz<yz.
题目讨论 (6条评论)

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emily666
n-10+n-2
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0 回复 2020-04-26 09:44:59
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Qiuyu
but together they have sold less than n boxes
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0 回复 2019-08-02 20:18:11
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盐饮
Mark sold 10 boxes less than n and Ann sold 2 boxes less than n--Mark sold n-10 boxes;Ann sold n-2 boxes; If Mark and Ann have each sold at least one box of cookies, but together they have sold less than n boxes--n-10>=1;n-2>=1;--n>=11;n>=3;2n-12
=11&n<=12--n=11 0
0 回复 2018-10-01 09:11:05
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stellabb
求解不等式的隐含表达:If Mark and Ann have each sold at least one box of cookies 即n-10大于等于1,n-2大于等于1,得n大于等于11;but together they have sold less than n boxes即 n-10+ n-2小于n,得n小于12。只有整数11符合
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0 回复 2018-01-19 16:04:46
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Brandi
Mark sold 10 boxes less than n and Ann sold 2 boxes less than n Mark 卖掉的是从n盒中减掉10盒后的数量 Ann卖掉的是从n盒中减掉2盒后的数量
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0 回复 2017-12-31 15:36:00
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花花iashin
Mark sold 10 boxes less than n 为什么可以解释为Mark卖了n-10个盒子?我理解的是,他卖了10个盒子,10
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0 回复 2017-11-08 11:38:37