WAEC - Further Mathematics (2017 - No. 24)
There are 7 boys in a class of 20. Find the number of ways of selecting 3 girls and 2 boys
1638
2730
6006
7520
Explicació
No of boys in the class = 7; Girls = 20-7 = 13
No of selection = \(^{13}C_{3} \times ^{7}C_{2} = \frac{13!}{(13-3)!3!} \times \frac{7!}{(7-2)!2!}\)
= \(286\times21 = 6006\)