標題:
發問:
1. A class has a total of 20 students of which five are male. If three students are chosen, in how many ways can at least 2 of the 3 are male students? 2. A team of 3 students are to be selected from a group of 4 boys and five girls to participate in a debate a) How many different teams of three can be... 顯示更多 1. A class has a total of 20 students of which five are male. If three students are chosen, in how many ways can at least 2 of the 3 are male students? 2. A team of 3 students are to be selected from a group of 4 boys and five girls to participate in a debate a) How many different teams of three can be formed? b) In how many ways that the team consists of exactly one boy and two girls?
最佳解答:
1. A class has a total of 20 students of which five are male. If three students are chosen, in how many ways can at least 2 of the 3 are male students? Sol: 2 male students ~ C153 × C52 ＝ 455 * 10 ＝ 4550 3 male student C152 × C53 ＝ 105 × 10 ＝ 1050 4550 ＋ 1050 ＝ 5600 Ans: 5600 ways 2. A team of 3 students are to be selected from a group of 4 boys and 5 girls to participate in a debate ( a ) How many different teams of three can be formed? ( b ) In how many ways that the team consists of exactly one boy and two girls? Sol: ( a ) C93 × C63 × C33 ÷ 3! ＝ 84 × 20 × 1 ÷ 6 ＝ 280 ( b ) (C31×C62) × (C21×C42) × (C11×C22) ÷ 3! ＝ (3*15) × (2*6) × (1*1) ÷ 6 ＝ 45 × 12 × 1 ÷ 6 ＝ 90 Ans: ( a ) 280 ways ( b ) 90 ways Send me a letter and tell me which step if you don’t understand.
其他解答:
1. 5600 ways 2. ( a ) 280 ways ( b ) 90 ways
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form 6 Permutaion and Combination, please help!發問:
1. A class has a total of 20 students of which five are male. If three students are chosen, in how many ways can at least 2 of the 3 are male students? 2. A team of 3 students are to be selected from a group of 4 boys and five girls to participate in a debate a) How many different teams of three can be... 顯示更多 1. A class has a total of 20 students of which five are male. If three students are chosen, in how many ways can at least 2 of the 3 are male students? 2. A team of 3 students are to be selected from a group of 4 boys and five girls to participate in a debate a) How many different teams of three can be formed? b) In how many ways that the team consists of exactly one boy and two girls?
最佳解答:
1. A class has a total of 20 students of which five are male. If three students are chosen, in how many ways can at least 2 of the 3 are male students? Sol: 2 male students ~ C153 × C52 ＝ 455 * 10 ＝ 4550 3 male student C152 × C53 ＝ 105 × 10 ＝ 1050 4550 ＋ 1050 ＝ 5600 Ans: 5600 ways 2. A team of 3 students are to be selected from a group of 4 boys and 5 girls to participate in a debate ( a ) How many different teams of three can be formed? ( b ) In how many ways that the team consists of exactly one boy and two girls? Sol: ( a ) C93 × C63 × C33 ÷ 3! ＝ 84 × 20 × 1 ÷ 6 ＝ 280 ( b ) (C31×C62) × (C21×C42) × (C11×C22) ÷ 3! ＝ (3*15) × (2*6) × (1*1) ÷ 6 ＝ 45 × 12 × 1 ÷ 6 ＝ 90 Ans: ( a ) 280 ways ( b ) 90 ways Send me a letter and tell me which step if you don’t understand.
其他解答:
1. 5600 ways 2. ( a ) 280 ways ( b ) 90 ways
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