The number of permutations of the 26 letters of the English alphabet that do not contain any of the strings fish, rat, or bird is 402619359782336797900800000
Let

Then

Note that since 
 ,
, 
But since
 ,
, 
and
 ,
 , 
Since

where 
and

What we are looking for is the number of permutations of the 26 letters of the alphabet that do  not contain the strings fish, rat or bird, or

This link contains another solved problem on permutations:
brainly.com/question/7951365
 
        
             
        
        
        
2) 60 because it's the one that appear the most
        
             
        
        
        
No, you divide 21.88 by 4.
        
                    
             
        
        
        
Answer:
2.17ft/s
Step-by-step explanation:
Look at the sketch of ladder at the beginning and after 3 seconds it starts to fall,
Distance of ladder from the wall 3 seconds after ladder starts to fall                                       =  Initial distance+  Velocity× time
= 6 + 2×3
= 12ft
Use trignometry to find out the speed of the top of ladder
cosθ= 12/20
θ= 0.825 rad
tan θ= v/2
v= 2.17ft/s
                                                                       
 
        
             
        
        
        
Answer:
Lots of "ifs" here.
A=bh/2 is the formula for the area of a triangle.
A=bh is the formula for the area of a rectangle or a parallelogram.
If the 6 & 4 area the base & height of a rectangle, then (6)(4) = 24 in^2
If the 6 & 10 are the base and height of a triangle, then 1/2(6)(10) = 30 in^2
Step-by-step explanation: