Answer:
a) 1/2
b) 1/n
c) 1/4
Step-by-step explanation:
a) For each permutation, either 1 precedes 2 or 2 precedes 1. For each permutation in which 1 precedes 2, we can swap 1 and 2 to obtain a permutation in which 2 preceds 1. Thus, half of the total permutations will involve in 1 preceding 2, hence, the probability for a permutation having 1 before 2 is 1/2.
c) If 2 is at the start of the permutation, then it is impossible for 1 to be before 2. If that is not the case, then 1 has a probability of 1/n-1 to be exactly in the position before 2. We can divide in 2 cases using the theorem of total probability,
P( 1 immediately preceds 2) = P (1 immediately precedes 2 | 2 is at position 1) * P(2 is at position 1) + P(1 immediately precedes 2 | 2 is not at position 1) * P(2 is not at position 1) = 0 * 1/n + (1/n-1)*(n-1/n) = 1/n.
d) We can divide the total of permutations in 4 different groups with equal cardinality:
- Those in which n precedes 1 and n-1 precedes 2
- those in which n precedes 1 and 2 precedes n-1
- those in which 1 precedes n and n-1 precedes 2
- those in which 1 precedes n and 2 precedes n-1
All this groups have equal cardinality because we can obtain any element from one group from another by making a permutations between 1 and n and/or 2 and n-1.
This means that the total amount of favourable cases (elements of the first group) are a quarter of the total, hence, the probability of the event is 1/4.
Answer:
A. The number of students that the club needs is at least (18).
Step-by-step explanation:
27 is the minimum requirement, so they need at <em>least</em><em> </em>18 people to meet said requirement. They can go over the limit.
The other answer comes into play if 27 was the <em>maximum</em><em> </em>that was allowed. Then they would need at most 18, because they can't admit any more people. They can't go over the limit.
Answer:
27:18
Step-by-step explanation:
multiply 3:2 by 9
Answer:
x = 5√3; y = 5
Step-by-step explanation:
Finding y: The sine function links the 30° angle, the 10 unit hypotenuse and the side opposite the angle, y:
sin 30° = 1/2 = y/10
Solve the equation of ratios
1 y
-- = ----- using cross-multiplication first: 2y = 10 → y = 5
2 10
We can now find x either by using a similar approach and the cosine function or by using the Pythagorean Theorem:
x² + y² = 10² = 100 → x² = 100 - y² = 100 - 5² = 75
If x² = 75, then x = ±√75 = ± (√25)·(√3) → ±5√3
Since lengths are always positive, take x = 5√3 as the answer.
Answer:
Yes.
Step-by-step explanation:
