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In a group of 6 boys and 4 girls, four children are to be selected.
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30 Jun 2018, 09:54
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In a group of 6 boys and 4 girls, four children are to be selected. In how many different ways can they be selected such that at least one boy should be there? A. 159 B. 208 C. 209 D. 212 E. 215
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Re: In a group of 6 boys and 4 girls, four children are to be selected.
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30 Jun 2018, 10:00



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Re: In a group of 6 boys and 4 girls, four children are to be selected.
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30 Jun 2018, 18:38
10 C 4 1 way to choose no boys 10 C 4  1 Answer C. 209



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Re: In a group of 6 boys and 4 girls, four children are to be selected.
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04 Jul 2018, 18:25
QZ wrote: In a group of 6 boys and 4 girls, four children are to be selected. In how many different ways can they be selected such that at least one boy should be there?
A. 159 B. 208 C. 209 D. 212 E. 215 We can use the equation: Total number of ways to select a group of 4 children  number of ways to select a group with no boys = number of was to select a group with at least 1 boy Total number of ways to select a group of 4 children is 10C4: 10C4 = 10!/(4! x 6!) = (10 x 9 x 8 x 7)/(4 x 3 x 2 x 1) = 10 x 3 x 7 = 210 Number of ways to select a group with no boys (i.e., all girls) is 6C0 x 4C4 = 1 x 1 = 1. Thus, the number of was to select a group with at least 1 boy is 210  1 = 209. Answer: C
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Re: In a group of 6 boys and 4 girls, four children are to be selected.
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07 Jul 2018, 01:34
Bunuel wrote: QZ wrote: In a group of 6 boys and 4 girls, four children are to be selected. In how many different ways can they be selected such that at least one boy should be there?
A. 159 B. 208 C. 209 D. 212 E. 215 (At least 1 boy) = (Total)  (0 boys, so all girls) (At least 1 boy) = 10C4  4C4 = 10!/(6!4!)  1 = 209. Answer: C. Thank you for the explanation Bunuel! However, could you please explain what is wrong in the below approach: atleast one guy  6C1 multiplied by 9C3  ways to select three people from the remaining 9. The above approach gives a wrong answer but i am unable to identify the error in logic. Please help!



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Re: In a group of 6 boys and 4 girls, four children are to be selected.
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07 Jul 2018, 07:40
agarwalaayush2007 wrote: Bunuel wrote: QZ wrote: In a group of 6 boys and 4 girls, four children are to be selected. In how many different ways can they be selected such that at least one boy should be there?
A. 159 B. 208 C. 209 D. 212 E. 215 (At least 1 boy) = (Total)  (0 boys, so all girls) (At least 1 boy) = 10C4  4C4 = 10!/(6!4!)  1 = 209. Answer: C. Thank you for the explanation Bunuel! However, could you please explain what is wrong in the below approach: atleast one guy  6C1 multiplied by 9C3  ways to select three people from the remaining 9. The above approach gives a wrong answer but i am unable to identify the error in logic. Please help! This way will give you duplication. Say, the boys are {1, 2, 3, 4, 5, 6} and girls are {a, b, c, d}. 6C1 gives you one boy from six, say {1}. 9C3 gives you three children from nine, say {2, 3, a}. So, the group is {1, 2, 3, a}. But we will get the same group in other ways too. For example: 6C1 can give you one boy from six, say {2}. 9C3 can give you three children from nine, say {1, 3, a}. So, the group is {1, 2, 3, a}. As you can see we got the same group of children.
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In a group of 6 boys and 4 girls, four children are to be selected.
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15 Jul 2018, 06:06
One can easily grasp these kinds of questions simply by imagining the concept on her/his own. What does it mean to have at least 1 boy? It means that the problem talks about 4 possible scenarios: 1 boy 3 girls, 2 boys 2 girls, 3 boys 1 girl, and 4 boys and no girl. So, 1st scenario: 6C1 * 4C3 2nd scenario: 6C2 * 4C2 3rd scenario: 6C3 * 4C1 4th scenario: 6C4 * 4C0 And finally, add these 4 and get the answer.
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Re: In a group of 6 boys and 4 girls, four children are to be selected.
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21 Jul 2018, 05:49
Bunuel wrote: QZ wrote: In a group of 6 boys and 4 girls, four children are to be selected. In how many different ways can they be selected such that at least one boy should be there?
A. 159 B. 208 C. 209 D. 212 E. 215 (At least 1 boy) = (Total)  (0 boys, so all girls) (At least 1 boy) = 10C4  4C4 = 10!/(6!4!)  1 = 209. Answer: C. Why we used 4C4 and not 4!. Isn't 4! ways to choose 4 people from a pool of the 4 people?
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Re: In a group of 6 boys and 4 girls, four children are to be selected.
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