Answer:

Step-by-step explanation:
The formula of a surface area of a ball (sphere):

R - radius
We have R = 15in. Substitute:

If you want to get an approximation, then:

 
        
             
        
        
        
Answer:
Step-by-step explanation:
Let assume that Suppose the chance of contracting malaria is 10% for those who are not vaccinated ;   (since the value) is not given.
Thus;
If the vaccine has no effect, risk of malaria for vaccine and no vaccine are equal to 0.1
Probability of not getting malaria if vaccinated or no vaccinated = 1 - 0.1 = 0.9
                           Malaria                No Malaria               Total
Vaccinated     100 * 0.1 = 10        100 * 0.9 = 90                         100
No Vaccine     200 * 0.1 = 20   200 * 0.9 = 180        300-100 = 200
Total                 20 + 10 = 30       90 + 180 = 270                       300
If the vaccine cuts the risk by half, risk of malaria for vaccinated are equal to 0.1/2 = 0.05
Probability of not getting malaria if vaccinated = 1 - 0.05 = 0.95
                           Malaria                No Malaria               Total
Vaccinated     100 * 0.05 = 5         100 * 0.95 = 95                 100
No Vaccine     200 * 0.1 = 20   200 * 0.9 = 180        300-100 = 200
Total                 20 + 5 = 25       90 + 180 = 275                         300
 
        
             
        
        
        
What is the question then I will see if I can help you find the answer