Step-by-step explanation:
wall 25×12=300
2 walls = 600
wall2 20×12=240
2 wall2= 480
600+480= 1080 sq ft
1/4 * 1/3 * 1/2 * 1/1 = 1/24 chance that all 4 letters are placed in the correct envelopes.
With the first envelope, there are 4 choices of letters, so the probability of picking the correct letter is 1/4.
With the second envelope, there are 3 remaining letters, so the probability of picking the correct letter is 1/3.
The same logic follows the the third and final letter.
Answer:
a) 
b) 
And replacing we got:

c) 


And adding we got:

Step-by-step explanation:
Previous concepts
The binomial distribution is a "DISCRETE probability distribution that summarizes the probability that a value will take one of two independent values under a given set of parameters. The assumptions for the binomial distribution are that there is only one outcome for each trial, each trial has the same probability of success, and each trial is mutually exclusive, or independent of each other".
Solution to the problem
Let X the random variable of interest, on this case we now that:
The probability mass function for the Binomial distribution is given as:
Where (nCx) means combinatory and it's given by this formula:
Assuming the following questions:
a. exactly five
For this case we can use the probability mass function and we got:

b. at least one
For this case we want this probability:

And we can use the complement rule and we got:


And replacing we got:

c. between four and six, inclusive.
For this case we want this probability:




And adding we got:

Answer:
30
Step-by-step explanation:
1 and 1/4 cup of raisins and 2 and 1/2 cups of nuts for a total of 3 and 3/4 cups.