2 years ago

Find the number of ways of selection 3 prefects in a class of 15 boys and 10 girls. If one of the prefects must be a girl.

Mathematics

1 answer:

UNO [17]2 years ago

3 0

Answer:

1845

Step-by-step explanation:

if one of the prefects must be a girl, the only allowed combinations are GBB, GGB, and GGG

GBB
(15c2 * 10c1) / 25c3 = 21/46
GGB
(15c1 * 10c2) / 25c3 = 27/92
GGG
(15c0 * 10c3) / 25c3 = 6 / 115

21/46 + 27/92 + 6 / 115 = 369 / 460 or 0.802...
25c3 = 2300 * 0.802... = 1845

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Find the number of ways of selection 3 prefects in a class of 15 boys and 10 girls. If one of the prefects must be a girl. ​

Find the number of ways of selection 3 prefects in a class of 15 boys and 10 girls. If one of the prefects must be a girl.