A) the elevator started at floor 12
B) it moved down 8 floors to floor 4
C) it stopped moving
D) it moved up 2 floors from floor 8 to floor 10
Answer:
The probability that the good exam belongs to student <em>X</em> is 0.8571.
Step-by-step explanation:
It is provided that the probability that <em>X</em> did well in the exam is, P (X) = 0.90 and the probability that <em>X</em> did well in the exam is, P (Y) = 0.40,
Compute the probability that exactly one student does well in the exam as follows:
![P(Either\ X\ or\ Y\ did\ well)=P(X\cap Y^{c})+P(X^{c}\cap Y)\\=P(X)P(Y^{c})+P(X^{c})P(Y)\\=P(X)[1-P(Y)]+[1-P(X)]P(Y)\\=(0.80\times0.60)+(0.20\times0.40)\\=0.56](https://tex.z-dn.net/?f=P%28Either%5C%20X%5C%20or%5C%20Y%5C%20did%5C%20well%29%3DP%28X%5Ccap%20Y%5E%7Bc%7D%29%2BP%28X%5E%7Bc%7D%5Ccap%20Y%29%5C%5C%3DP%28X%29P%28Y%5E%7Bc%7D%29%2BP%28X%5E%7Bc%7D%29P%28Y%29%5C%5C%3DP%28X%29%5B1-P%28Y%29%5D%2B%5B1-P%28X%29%5DP%28Y%29%5C%5C%3D%280.80%5Ctimes0.60%29%2B%280.20%5Ctimes0.40%29%5C%5C%3D0.56)
Then the probability that <em>X</em> is the one who did well in the exam is:
![P(X\ did\ well\ in\ the\ exam)=\frac{P(X\cap Y^{c})}{P(X\cap Y^{c})+P(X^{c}\cap Y)}\\ =\frac{P(X)[1-P(Y)]}{P(X\cap Y^{c})+P(X^{c}\cap Y)} \\=\frac{0.80\times0.60}{0.56}\\=0.857143\\\approx0.8571](https://tex.z-dn.net/?f=P%28X%5C%20did%5C%20well%5C%20in%5C%20the%5C%20exam%29%3D%5Cfrac%7BP%28X%5Ccap%20Y%5E%7Bc%7D%29%7D%7BP%28X%5Ccap%20Y%5E%7Bc%7D%29%2BP%28X%5E%7Bc%7D%5Ccap%20Y%29%7D%5C%5C%20%3D%5Cfrac%7BP%28X%29%5B1-P%28Y%29%5D%7D%7BP%28X%5Ccap%20Y%5E%7Bc%7D%29%2BP%28X%5E%7Bc%7D%5Ccap%20Y%29%7D%20%5C%5C%3D%5Cfrac%7B0.80%5Ctimes0.60%7D%7B0.56%7D%5C%5C%3D0.857143%5C%5C%5Capprox0.8571)
Thus, the probability that the good exam belongs to student <em>X</em> is 0.8571.
There are two ways to find the answer. You could use cross-product or common denominator. To get the common denominator, change the denominators to 12 by multiplying both sides of 2/3 by 4. This gives you 8/12. 8/12 is less than 11/12.
Cross-product is easier and more time saving than changing into common denominators, though. In order to do this, set up your fractions vertically. Multiply the numerator of the first by the denominator of the second. Place the product above the second fraction. Then, multiply the numerator of the second fraction by the denominator of the first. Next, place the product above the first fraction. Then compare the two products. Whichever fraction has the greater number on top is the greater fraction. To do this, 11x3 is 33. Write that over 2/3. 2x12 is 24. Write that over 11/12. Since 33 is greater than 24, 2/3 is greater.
The final answer is: 11/12<2/3.
Answer:
D
Step-by-step explanation:
Answer: 144ft
Step-by-step explanation: Hope this help :D
