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Sia

Question
Math
Posted about 1 month ago
这道题答案是2026 答案错了
解答这道题
一副二色牌共有纸牌22张,其中红,蓝每种颜色各 11 张,编号分别为 0,1 , 2,,102, \ldots, 10 ,从这副牌中任取若干张牌,然后按照如下规则计算分值:每张编号为 kk 的牌记为 2k2^{k} 分,若它们的分值之和为2025,就称这些牌为一个"好"牌组,则"好"牌组的个数为 \qquad
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Answer from Sia
Posted about 1 month ago
Solution by Steps
step 1
We need to find the number of subsets of the cards such that the sum of their values equals 2025. Each card with number k k contributes 2k 2^k points. The values of the cards are 20,21,22,,210 2^0, 2^1, 2^2, \ldots, 2^{10}
step 2
The total value of all cards is given by the sum 20+21+22++210=2111=2047 2^0 + 2^1 + 2^2 + \ldots + 2^{10} = 2^{11} - 1 = 2047
step 3
To find subsets that sum to 2025, we can calculate 20472025=22 2047 - 2025 = 22 . This means we need to find subsets of cards that sum to 22
step 4
The value 22 can be represented as a sum of powers of 2. The binary representation of 22 is 101102 10110_2 , which corresponds to 24+23+21 2^4 + 2^3 + 2^1 . Thus, we can use the cards numbered 1, 3, and 4
step 5
The number of ways to select cards is determined by the combinations of the remaining cards. Since we have 11 cards of each color, we can choose any combination of the remaining cards. The total number of combinations is 23=8 2^3 = 8 (including the empty set)
Answer
The number of "good" card groups is 8.
Key Concept
The problem involves finding subsets of a set that sum to a specific value using powers of 2.
Explanation
The solution involves calculating the total value of the cards and determining which combinations can achieve the target sum of 2025. The binary representation helps identify the necessary cards.

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