Answer:
The  90 % confidence  interval  for the mean population is (11.176  ; 20.824 )
Rounding to at least two decimal places would give 11.18 , 20.83 
Step-by-step explanation:
Mean = x`= 16 miles per hour
standard deviation =s= 4.1 miles per hour
n= 4
 =  4.1/√4= 4.1/2= 2.05
  =  4.1/√4= 4.1/2= 2.05
1-α= 0.9
degrees of freedom =n-1=  df= 3
∈ ( estimator  t with 90 % and df= 3 from t - table ) 2.353
 Using Students' t - test 
x`±∈ * 
Putting values 
16 ± 2.353 * 2.05
= 16 + 4.82365
20.824  ;        11.176
The  90 % confidence  interval  for the mean population is (11.176  ; 20.824 ) 
Rounding to at least two decimal places would give 11.18 , 20.83
 
        
                    
             
        
        
        
Answer:
  L  = 2r  + 3
Step-by-step explanation:
Given parameters: 
Area of rectangle  = 14r + 21 
Width of the rectangle  = 7ft
Unknown: 
Length of the rectangle  = ? 
Solution: 
If the length of the rectangle is designated as L; 
  Area of a rectangle = Length x width 
 Now insert the parameters: 
            14r + 21   = L x 7 
             L  =  
  
             L  = 2r  + 3
 
        
             
        
        
        
Answer:
total area = 217 m³
Step-by-step explanation:
area of the triangle
= 14 × 10
= 140 m²
area of a semicircle
= 1/2 × 22/7 × 7 × 7
= 77 m²
total area
= 140 + 77
= 217 m³
 
        
             
        
        
        
I think B. Would be the answer