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

=> 
9514 1404 393
Answer:
60 cm
Step-by-step explanation:
July and August are 2 of the 12 months in the year. The growth for the year can be expected to be 6 times the growth in a 2-month period, so 60 cm.
_____
You could get down to particulars as to the number of days in those two months versus the total number of days in a year. You would have to specify whether it is a leap year. In a non-leap year, the growth might be ...
365/(31+31) × 10 cm ≈ 58.9 cm
In a leap year, it would be 59.0 cm.
Answer:
see the explanation
Step-by-step explanation:
Let
x ---> kilograms of cement needed
y ----> kilograms of sand needed
z ----> kilograms of gravel needed
we know that
----> 

Divide 480 by 8
----> scale factor
Multiply the scale factor by the ratio 
<em>Find out the kilograms of cement needed</em>

<em>Find out the kilograms of sand needed</em>

<em>Find out the kilograms of gravel needed</em>

1
It's whole number
So I think it's the answer