Answer:
 
Step-by-step explanation:
The given data set is:
Week 1: 600	
Week 2: 300	
Week 3: 500	
Week 4: 900
The following are the steps to find the standard deviation:
Step 1. Jim enters the data and calculates the average or mean. 

Step 2. Jim calculates the deviation from the mean by subtracting the mean from each value. 
Data value (x)                                                             
600                                                                           25
300                                                                         -275
500                                                                         -75
900                                                                          325
Step 3. Jim squares each deviation to remove negative signs.
Data value (x)                                                           
600                                                                       625
300                                                                    75625
500                                                                      5625
900                                                                   105625
Step 4. Jim sums the squares of each deviation and divides by the count for the variance. 

Step 5.Jim takes the square root of the variance to find the standard deviation.

 
        
                    
             
        
        
        
Answer:
<D is correct its confusing on the solving but 
Step-by-step explanation:
 
        
             
        
        
        
Answer:
120 people
Step-by-step explanation:
Length of dance floor = 30 ft
Width of dance floor = 20 ft
Given that 2 people will occupy 5 ft² of space, the number of people that will crowd the floor of the dance floor is calculated as follows:
= Area of dance floor ÷ 5 ft²
= (30*20) ÷ 5
= 600 ÷ 5 
= 120.
120 people will crowd the dance floor.
 
        
             
        
        
        
12/21 in its simplest form is 4/7.
To find this out we need to divide the numerator and denominator by the GCF of 12 and 21 which is 3.
12/21
12 ÷ 3 = 4
21 ÷ 3 = 7
4/7
12/21 in its simplest form is 4/7.
12/21 = 4/7
        
                    
             
        
        
        
I think the first one might be 18 second might be 10