Answer:
a) The mean number of radioactive atoms that decay per day is 81.485.
b) 0% probability that on a given day, 50 radioactive atoms decayed.
Step-by-step explanation:
Poisson distribution:
In a Poisson distribution, the probability that X represents the number of successes of a random variable is given by the following formula:
In which
x is the number of sucesses
e = 2.71828 is the Euler number
is the mean in the given interval.
a. Find the mean number of radioactive atoms that decayed in a day.
29,742 atoms decayed during 365 days, which means that:
The mean number of radioactive atoms that decay per day is 81.485.
b. Find the probability that on a given day, 50 radioactive atoms decayed.
This is P(X = 50). So
0% probability that on a given day, 50 radioactive atoms decayed.
FOUND THE COMPLETE QUESTION IN ANOTHER SOURCE.ATTACHED IMAGE. For this case what we have is the following:
For the two semicircles we can model it as a complete circle.
We have to then:
Perimeter:
P = 2 * pi * r
or
P = pi * d
Where,
r = radius
d = diameter
Therefore the perimeter is:
P = 10 * pi
For the largest circle we have:
radius = 10
Perimeter:
P '= 2pi10
P '= 20pi
1/4 since 1/4 circle:
P '' = 20pi / 4 = 5pi
Then, the total perimeter of the source is:
Pt = P + P '' = 10pi + 5pi = 15pi
Pt = 15 * (3.141592)
Pt = 47.1239
round
Pt = 47.1 ft
Area:
The total area will be:
A = A (two semicircles) + A (quarter big circle)
A = (pi / 4) * (d ^ 2) + (1/4) * pi * r ^ 2
A = (pi / 4) * ((10) ^ 2) + (1/4) * pi * (5) ^ 2
A = 98.17477042 feet ^ 2
Round:
A = 98.2 feet ^ 2
Answer:
Perimeter of the source:
Pt = 47.1 ft
Area of the source:
A = 98.2 feet ^ 2
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Let the number be (10 x + y)
Then, 10 x + y = 3 * (x + y) (given)
Or, 10 x + y = 3 x + 3 y
Or, 10 x - 3 x = 3 y - y
Or, 7x = 2 y
Or, x = 2 y / 7 ( Eq. 1)
Also, 10 x + y + 45 = 10 y + x ( given)
Or, 10 x - x = 10 y - y - 45
Or, 9 x = 9 y - 45 ( Eq. 2)
Substituting the value of x from (Eq. 1) in (Eq. 2), we have:
9 * 2 y / 7 = 9 y - 45
Or, (9 y ) - (18 y / 7) = 45
Or, 63 y - 18 y = 315
Or, 45 y = 315
Or, y = 7
From (Eq. 1),
x = 2 * 7 / 7 = 2
So, the number is 10 x + y = (10 * 2) + 7 = (20 + 7) = 27
Answer
Check:
Sum of the digits = 2 + 7 = 9
9 * 3 = 27 ✓
Adding 45 to the number 27, we get 72. So, the digits get reversed.
5*2 = 10
10*1 = 10
Hope I helped
