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Katarina [22]
2 years ago
13

On the island of liars each inhabitant lies with probability 2/3. You overhear an inhabitant making a statement. Next you ask an

other inhabitant whether the inhabitant you overheard spoke truthfully. Use Bayes rule to find the probability that the inhabitant you overheard indeed spoke truthfully given that the other inhabitant says so
Mathematics
1 answer:
bonufazy [111]2 years ago
7 0

Answer:

The probability that the inhabitant spoke thruthfully given than the other one says so is 1/4.

Step-by-step explanation:

Let A be the event 'the first inhabitant speaks the truth' and B the event the person you asked speaks the truth'

We have that

P(A) = P(B) = 1/3

The second person will say that the first person speaks the truth if:

- Both are lying

- Both are saying the truth

The probability that both inhabitants lies is 2/3 * 2/3 = 4/9

The probability that both inhabitants speaks the truth is 1/3² = 1/9

Therefore, in this problem, we want to know P(A ∩ B | (A∩ B) ∪ (A^c ∩ B^c) )

(note that, since the second persons says that A didnt lie, then in order for it to be true then the second person have to also say the truth).

We know that P(A ∩ B) = 1/9 and P((A∩ B) ∪ (A^c ∩ B^c)) = 4/9 + 1/9 = 5/9. Using the bayes formula we have

P(A ∩B | (A∩ B) ∪ (A^c ∩ B^c) ) = P((A∩ B) ∪ (A^c ∩ B^c) | A ∩ B) * P(A∩ B)/ P((A∩ B) ∪ (A^c ∩ B^c))

Note that P((A∩ B) ∪ (A^c ∩ B^c) | A∩B) = 1 because the condition is more restrictive than the probability we are asking for, therefore

P(A ∩B | (A∩ B) ∪ (A^c ∩ B^c) )  = P(A∩ B)/P((A∩ B) ∪ (A^c ∩ B^c))  = (1/9) / (4/9) = 1/4.

The probability that the inhabitant spoke thruthfully given than the other one says so is 1/4.

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2 years ago
The selling price of a chair is N14 000. The trader gives a 25% discount for cash. What is the cash price?
True [87]

Answer:N10500

Step-by-step explanation:

10%of 14000=1400

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hope this helps

5 0
2 years ago
A rectangular portrait measures 50cm by 70cm. It is surrounded by a rectangular frame of uniform width. If the area of the frame
snow_tiger [21]

Let us assume uniform width = x cm wide.

Length of rectangular portrait = 50cm and width of rectangular portrait = 70cm.

Therefore,  length of rectangle made by frame = 50 + x+x = (2x+50) cm.

And width of rectangle made by frame = 70+x+x = (2x+70) cm.

We know, the area of rectangular portrait = 50 × 70 = 3500 cm^2.

Total area of the rectangle made by frame would be =  (2x+50) * (2x+70)

We know,

Actual area of frame = Area of rectangle made by frame -  area of rectangular portrait.

We also given "the area of the frame is the same as the area of the portrait."

We can setup an equation now,

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Subtracting 3500 from both sides, we get

3500-3500 = (2x+50) * (2x+70) - 3500-3500.

0 = (2x+50) * (2x+70) -7000.

FOIL (2x+50) * (2x+70), we get

0 = 2x*2x +2x*70 + 50*2x +50*70 - 7000.

0 = 4x^2 +140x +100x +3500 -7000.

4x^2 +240x -3500 = 0.

Dividing whole equation by 4, we get

x^2 +60x - 875 =0

Applying quadratic formula =\frac{-b\pm \sqrt{b^2-4ac}}{2a}, we get

=\frac{-60\pm \sqrt{60^2-4\cdot \:1\left(-875\right)}}{2\cdot \:1}

x=\frac{-60+\sqrt{60^2-4\cdot \:1\left(-875\right)}}{2\cdot \:1}=5\left(\sqrt{71}-6\right)

x=\frac{-60-\sqrt{60^2-4\cdot \:1\left(-875\right)}}{2\cdot \:1}:\quad -5\left(6+\sqrt{71}\right)

We cant take negative value.

So, x=5\left(\sqrt{71}-6\right)=12.13

We could take approximately 12 cm.



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2 years ago
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I hope that's the answer.

7 0
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