If you have a fraction, take one number and put a different number on top or underneath, for example if you have 2 cats and 3 dogs, the ratio from cats to dogs would be 2:3 but if you did 2 cats to the total number of animals, you would add 2 and 3 and get 5, so the ratio would be 2:5.
Answer:
Expected time is 15 hours for him to get to safety.
Step-by-step explanation:
We define X as the time that this miner would get to safety.
We define Y as the door he chooses initially.
P(Y= 1) = P(Y=2)=P(Y=3) = 1/3
We have E[X|Y=1] = 3
E[X|Y] = 5 hours + E[X}
E[X|Y] = 7 hours + E[X]
Then we have
E[X] = 1/3(3 + 5 + E[X] + 7 + E[X])
We cross multiply
3*E[X] = (15 + 2E[x])
3E[X] - 2E[X] = 15
E[X] = 15
So the time it would take to get him to safety is 15 hours
IF USING GEOMETRY...
x-axis = (x, -y)
Because the x does not have a negative sign the number DOES NOT change to its opposite form, but because the y has a negative sign the number DOES changes to its opposite form (from negative number to positive.)
So... if we use the formula of x-axis, which is (x, -y), the coordinates (-7,-3) would change to (-7, 3)
ANSWER (-7, 3)
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