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aleksley [76]
3 years ago
12

What is the probability of these events when we randomly select a permutation of {1,2, ..., n} where n≥4? a) 1 precedes 2 c) 1 i

mmediately precedes 2 d) n precedes 1 and n−1 precedes 2
Mathematics
1 answer:
Paraphin [41]3 years ago
3 0

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.

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An airplane leaves an airport and flies due west 150 miles and then 170 miles in the direction S 49.17°W. How far is the plane f
Ganezh [65]

Answer:

299.99 miles

Step-by-step explanation:

Since the plane traveled due west,

The total angle is 49.17 + 90

Represent that with θ

θ = 49.17 + 90

θ = 139.17.

Represent the sides as

A = 170

B = 150

C = unknown

Since, θ is opposite side C, side C can be calculated using cosine formula as;

C² = A² + B² - 2ABCosθ

Substitute values for A, B and θ

C² = 150² + 170² - 2 * 150 * 170 * Cos 139.17

C² = 22500 + 28900 - 51000 * Cos 139.17

C² = 51400 - 51000 (−0.7567)

C² = 51400 + 38,591.7

C² = 89,991.7

Take Square Root of both sides

C = 299.9861663477167

C = 299.99 miles (Approximated)

Hence, the distance between the plane and the airport is 299.99 miles

8 0
4 years ago
Sam is walking across a bridge and accidentally drops an orange into the river basin below
irina1246 [14]

Answer:

We assume that the orange is dropped at t = 0s.

Once the orange is on the air, the only force acting on it is the gravitational force, then the acceleration of the orange is the gravitational acceleration.

A(t) = -32.17 ft/s^2

Where the negative sign is because this acceleration points downwards.

For the velocity equation, we need to integrate over time, we will get:

V(t) = (-32.17 ft/s^2)*t + V0

Where V0 is the initial vertical velocity of the orange, because the orange is accidentally dropped, this initial velocity is equal to zero.

V(t) =   (-32.17 ft/s^2)*t

For the position equation we need to integrate again, this time we get:

P(t) = (1/2)*(-32.17 ft/s^2)*t^2 + P0

Where P0 is the initial height of the orange, we know that it is 40ft, then the position equation is:

P(t) =  (1/2)*(-32.17 ft/s^2)*t^2 + 40 ft

Now that we know the equation, we can graph it. (you can see the graph below)

Now we also want to find at what time does the orange hit the water.

This happens when:

P(t) = 0 ft =   (1/2)*(-32.17 ft/s^2)*t^2 + 40 ft

We just need to solve that equation for t.

0 ft =   (1/2)*(-32.17 ft/s^2)*t^2 + 40 ft

(1/2)*(32.17 ft/s^2)*t^2 =  40 ft

t^2 = (40ft)/( (1/2)*(32.17 ft/s^2))

t = √(  (40ft)/( (1/2)*(32.17 ft/s^2)) ) = 1.58 s

The orange hits the water 1.58 seconds after it is dropped.

3 0
3 years ago
I am really confused on questions 1-5 can you please help?????
Norma-Jean [14]
I can answer 1 it would be 2.5x+5y=20
5 0
3 years ago
A-15=4a-3<br> if u dont want spam then dont answer
balu736 [363]

Answer:

they deleted my answer :(

Step-by-step explanation:

7 0
3 years ago
Lucy has 270 green crayons and 360 brown crayons. If she
ruslelena [56]

Answer:

15 more bags.

Step-by-step explanation:

360/6= 60.

270/6=45

60-45=15.

Hope this helps. <3

4 0
3 years ago
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