3/4 of the 8th graders at kingston middle school went on the class trip. if 252 students went in the trip, how many 8th graders
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Answer:
Step-by-step explanation:
The total number of permutations of boys and girls on the team are:
¹⁶P₅*¹³P₄
1.
Bob will be one of the fixed boys to be picked. Hence, actually 4 boys are to be picked from 15. The permutations of girls being picked remains the same.
Probability = Permutations with Bob as one of the boys / Total permutations
Probability = (¹⁵P₄*¹³P₄) / (¹⁶P₅*¹³P₄) = ¹⁵P₄ / ¹⁶P₅
Probability = = 15! / 16! = 1/16
2.
Now, Bob is one of the fixed boys and Jane is one of the fixed girls. Hence, actually 4 boys are to be picked from 15 and 3 girls are to be picked from 12.
Probability = Permutations with bob as one of the boys and jane as one of the girls / Total permutations
Probability = (¹⁵P₄*¹²P₃) / (¹⁶P₅*¹³P₄) = (1/16)*(1/13) = 1/208
3.
Now, the probability that at least Jane or Bob will be picked has been asked. This probability is a combination of three probabilities:
Probability = (Probability that only Bob will be picked) + (Probability that only Jane will be picked) + (Probability that both will be picked)
Probability = 1/16 + 1/13 + 1/208 = 0.123
4.
Total teams possible = ¹⁶P₅*¹³P₄ = 8994585600 teams are possible