Step-by-step explanation:
Area of a circle = #r^2
1256 = 3.14 × r^2
r^2 = 1256/3.14
r^2 = 400
Square root of r = 20
Diameter = 2 × r = 2 × 20 = 40 inches
Answer:
a

b

Step-by-step explanation:
From the question we are told that
The mean value is 
The standard deviation is 
Considering question a
The sample size is n = 9
Generally the standard error of the mean is mathematically represented as

=>
=> 
Generally the probability that the sample mean hardness for a random sample of 9 pins is at least 51 is mathematically represented as



=> 
From the z table the area under the normal curve to the left corresponding to 2.5 is

=> 
=> 
Considering question b
The sample size is n = 40
Generally the standard error of the mean is mathematically represented as

=>
=> 
Generally the (approximate) probability that the sample mean hardness for a random sample of 40 pins is at least 51 is mathematically represented as

=> 
=> 
From the z table the area under the normal curve to the left corresponding to 5.2715 and
=> 
So

=> 
Answer:
$400 at 4% per year
Step-by-step explanation:
because then you put 400 and use the formula of interest you can see which gives bigger
Answer:
C (7 hours)
Step-by-step explanation:
366 divided by 6 = 61
(This proves they are going 61 mph)
427 divided by 7 = 61