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   DinarGuru

To solve this problem, we can start by listing all the possible outcomes of flipping a fair coin two times:

HH (two heads)

HT (one head, one tail)

TH (one tail, one head)

TT (two tails)

We can then calculate the length of the longest run for each outcome:

HH: The longest run is 2.

HT: The longest run is 1.

TH: The longest run is 1.

TT: The longest run is 2.

Therefore, the expected length of the longest run is the average of the longest runs for each outcome:

Expected longest run = (2 + 1 + 1 + 2) / 4 = 1.5

So the expected length of the longest run when flipping a fair coin two times is 1.5.

Feb 20, 2023
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Feb 20, 2023
Feb 19, 2023
 #1
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Let's label the points in the diagram as follows:

The vertices of the parallelogram are A, B, C, and D, with AB parallel to CD and AD parallel to BC.

The points where the parallel lines intersect the sides of the parallelogram are E, F, G, and H, as shown in the diagram.

The side length of the equilateral triangle is s.

Since the three regions have the same area, the area of each region is 1/3 of the total area of the parallelogram. Let's denote the area of the parallelogram as A.

The area of the equilateral triangle is (s^2√3)/4, and since it is one of the regions, we know that:

(s^2√3)/4 = A/3

Simplifying this equation, we get:

s^2 = 4A/(3√3)

Now, let's look at the parallelogram as a whole. Since AB is parallel to CD, we know that triangle AEF is similar to triangle BGF, and since AD is parallel to BC, we know that triangle ADE is similar to triangle BCF. This means that:

AE/EB = BF/FG AD/DE = BC/CF

Let's use these ratios to express AE, BF, AD, and BC in terms of s:

AE = s/3 (since the perimeter of the equilateral triangle is 1) EB = 2s/3 BF = 2s/3 FG = s/3 AD = (2s + 2EB)/3 = (2s + 4s/3)/3 = 10s/9 DE = (2s + 2AE)/3 = (2s + 2s/3)/3 = 8s/9 BC = (2s + 2FG)/3 = (2s + s/3)/3 = 7s/9 CF = (2s + 2BF)/3 = (2s + 4s/3)/3 = 10s/9

Now we can find the perimeter of the parallelogram:

Perimeter = 2(AB + AD) = 2(EB + BC) = 2(2s/3 + 7s/9) = 4s/3 + 14s/9 = (22s/9)

Substituting s^2 = 4A/(3√3) from the earlier equation, we get:

Perimeter = (22/9) sqrt(3)

 

So the perimeter of the original parallelogram is 22/9*sqrt(3).

Feb 19, 2023
 #2
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Feb 19, 2023
Feb 18, 2023

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