Answer:
A) 0.99413
B) 0.00022
Step-by-step explanation:
A) First of all let's find the total grading time from 6:50 P.M to 11:00 P.M.:
Total grading time; X = 11:00 - 6:50 = 4hours 10minutes = 250 minutes
Now since we are given an expected value of 5 minutes, the mean grading time for the whole population would be:
μ = n*μ_s ample = 42 × 5 = 210 minutes
While the standard deviation for the population would be:
σ = √nσ_sample = √(42 × 6) = 15.8745 minutes
To find the z-score, we will use the formula;
z = (x - μ)/σ
Thus;
z = (250 - 210)/15.8745
z = 2.52
From the z-distribution table attached, we have;
P(Z < 2.52) ≈ 0.99413
B) solving this is almost the same as in A above, the only difference is an additional 10 minutes to the time.
Thus, total time is now 250 + 10 = 260 minutes
Similar to the z-formula in A above, we have;
z = (260 - 210)/15.8745
z = 3.15
P(Z > 3.15) = 0.00022
Example of use of terms:
Statement: If it is far, we take a bus.
Inverse: If it is not far, we do not take a bus.
Converse: If we take a bus, it is far.
Contrapositive: If we do not take a bus, it is not far.
We also know that
1. The inverse of the inverse is the statement itself, and similarly for converse and contrapositive.
2. Only the contrapositive is logically equivalent to the original statement.
This means that the converse and inverse are logically different from the original statement.
Now back to the given statement.
To find the original statement, we find the contrapositive of the contrapositive.
We then find the converse from the original statement, as in the example above.
Original statement
(note that in English, if it is not worth X dollars, means if it is not worth AT LEAST X dollars")
contrapositive of
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"If an item is not worth five dimes, then it is not worth two quarters.”
is the negation of the converse, which become
"If an item is worth two quarters, then it is worth (at least) five dimes."
The converse of the previous statement is therefore
"If an item is worth (at least) five dimes then it is worth two quarters"
In this particular case, we can also take advantage of the fact that the contrapositive is the negation of the converse. So all we have to do is the provide the negation of each component of the contrapositive to get the converse:
"If an item is worth (at least) five dimes, then it is worth two quarters".
as before.
Note that the converse does NOT logically mean the same as the original statement.
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The general formula for exponential growth and decays is:

if k>0 then then it is an exponential growth function. If k<0 then the function represents an exponential decay.
Now we need to classify each of the functions:
1.
The function

can be wrtten as:

comparing with the general formula we notice that k=2, therefore this is an exponential growth.
2.
The function

can be written as:

comparing with the general formula we notice that k=-4, therefore this is an exponential decay.
3.
The function

comparing with the general formula we notice that k=-1, therefore this is an exponential decay.