Answer:
11.42 boxes
Step-by-step explanation:
For the first box bought, there is a 100% chance of getting a unique toy (since you still don't have any). E₁ = 1.
After that, there is a 4 in 5 chance of getting a unique toy from the next box, the expected number of boxes required is:

For the next unique toy, there is now a 3 in 5 chance of getting it:

Following that logic, there is a 2 in 5 chance of getting the 4th unique toy:

Finally, there is a 1 in 5 chance to get the last unique toy:

The expected number of boxes to obtain a full set is:

 
        
             
        
        
        
1/2r - 3 = 3(4-3/2) -----> Simplify the right side.
1/2r - 3 = 3(1/2) -----> Multiply 
1/2r - 3 = 3/2 ----> Add 3 to both sides
1/2r = 6/2 + 3/2 
1/2r = 9/2 -----> Divide both sides by 1/2 which is the same as multiplying my 2
r = 18/2
r = 9
Hope this helps!
        
             
        
        
        
Answer:
what is the question? it's not clear
 
        
             
        
        
        
Answer:
0.06
Step-by-step explanation:
 
        
                    
             
        
        
        
Answer:
I am 1 year boy i dont know