In a group of 15 students there are 6 scouts In how many ways can 12 be selected so as to include exactly 4 scouts
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Total no. of students = 15
No. of scouts in the group of 15 students = 6.
No. of ways of selection of 6 scouts from the group = ¹⁵C₆
No. of ways of selection of 4 scouts from 6 scouts = ⁶C₄
∴ No. of ways of selection of 12 student from 15 students so as to include exactly 4 scouts = ¹⁵C₆ × ⁶C₄ × ¹⁵⁻⁶C₈ = ¹⁵C₆ × ⁶C₄ × ⁹C₈ = 675675 ways
No. of scouts in the group of 15 students = 6.
No. of ways of selection of 6 scouts from the group = ¹⁵C₆
No. of ways of selection of 4 scouts from 6 scouts = ⁶C₄
∴ No. of ways of selection of 12 student from 15 students so as to include exactly 4 scouts = ¹⁵C₆ × ⁶C₄ × ¹⁵⁻⁶C₈ = ¹⁵C₆ × ⁶C₄ × ⁹C₈ = 675675 ways
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