Answer:
b. quadruple the sample size.
Step-by-step explanation:
Given that a 95% confidence is given by (15,20) .
this implies that mean = average of lower and higher bounds of confidence interval = 
Margin of error = Upper bound - Mean = 
Confidence level = 95%
Critical value = 1.96
Std error = 
Std devition = Std error * sqrt n = 6.3775
If we want to reduce margin of error by half we must get margin of error as 1.25
For that std error for same critical value = 0.63775
Std deviation did not change
So sample size only changed which implies that sample size is 4 times the original
b. quadruple the sample size.
I'll assume the ODE is
Solve the homogeneous ODE,
The characteristic equation
has roots at 
and 
. Then the characteristic solution is
For nonhomogeneous ODE (1),
consider the ansatz particular solution
Substituting this into (1) gives
For the nonhomogeneous ODE (2),
take the ansatz
Substitute (2) into the ODE to get
Lastly, for the nonhomogeneous ODE (3)
take the ansatz
and solve for 
.
Then the general solution to the ODE is
To calculate for area given the circumference we proceed as follows:
C=2πr
where:
r=radius
thus given that C=25 1/7 in=176/7
thus plugging in our formula to solve for r we get:
176/7=2πr
thus
r=4.002~4.00 in
hence the area will be:
A=πr²
A=π×(4²)
A=50 2/7 in²
