Direction: Read the following text and answer the following questions...
Solution:
Given:
- Polio drops are delivered to 50K children in a district.
- The rate at which polio drops are given is directly proportional to the number of children who have not been administered the drops.
- By the end of the 2nd week, half the children have been given the polio drops.
To find:
- The number of children who will have been given the drops by the end of the 3rd week.
Let's analyze the given information and solve the differential equation to find the solution.
1. Analyzing the given information:
- We are given that the rate at which polio drops are given is directly proportional to the number of children who have not been administered the drops.
- This means that the rate of administration of drops is proportional to the number of children remaining without drops, which can be represented as dy/dx = k(50 - y), where x denotes the number of weeks and y denotes the number of children who have been given the drops.
- By the end of the 2nd week, half the children have been given the polio drops. This means y = 50K/2 = 25K.
2. Solving the differential equation:
To solve the differential equation dy/dx = k(50 - y), we need to separate variables and integrate both sides.
dy/(50 - y) = k dx
Integrating both sides:
∫(1/(50 - y)) dy = ∫k dx
ln|50 - y| = kx + C1, where C1 is the constant of integration.
Now, let's solve for y:
|50 - y| = e^(kx + C1)
|50 - y| = e^(kx) * e^(C1)
Since e^(C1) is just another constant, let's denote it as C2:
|50 - y| = C2 * e^(kx)
3. Applying the initial condition:
By the end of the 2nd week, half the children have been given the polio drops, which means y = 25K. Substituting this value into the equation:
|50 - 25K| = C2 * e^(2k)
Since C2 is just a constant, let's denote it as C:
|50 - 25K| = C * e^(2k)
4. Simplifying the equation:
The absolute value expression can be written as two separate equations:
50 - 25K = C * e^(2k) (when 50 - 25K ≥ 0)
25K - 50 = C * e^(2k) (when 50 - 25K < />
5. Finding the value of C:
Since we know that y = 25K by the end of the 2nd week, we can substitute this value into one of the equations to find C:
25K - 50 = C * e^(2k)
25K = C * e^(2k) + 50
25K = C * 1 + 50 (since e^0 = 1)
25K = C + 50
C = 25K - 50
6. Writing the solution:
Substituting the value of C back into the equation:
|50 - 25K| = (25K - 50) * e
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