CSCI 110, Spring 2011

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Solutions for Review sheet for 1st midterm

Practice Problems
The following problems are intended to help you study for the exam.

1)Given these boolean variables:
x = true, y = false, z = true

What is the value (true/false) of each of the following?

i)  x and (y or z)

Answer:	True

ii) (not x) or  (not(y and z))

Answer:	True

iii) y or (x and not z)

Answer:	False

2)Consider a program that does the following:
Prompt the user to input a number between 0 and 100.
Input the number from the keyboard
If the number is greater than 50 and less than 100  write:
	XX is in the top 50 percent.
where XX refers to the number inputted by the user.
Otherwise, if the number is less than or equal to 50 write:
	XX is in the bottom 50 percent.
Otherwise, write
	Illegal number entered.
	
a) Draw a decision tree for the program.
(solution given in class)



b) Write a Python program to execute the program

#Program lowOrHigh.py
number = input("Enter a number between 0 and 100: ")
if number > 50 and number < 100:
	print number, "is in the top 50 percent."
elif number <= 50:
	print number, "is in the bottom 50 percent."
else:
	print "Illegal number entered."


3)  Compute the value of the following expressions:
a)  6 / 3 * 2

Answer: 4

b) (17 - 11) / 3 + 3

Answer: 5

c) Add parentheses to part b so that the addition is performed
before the division.

Answer: (17 - 11) / (3 + 3)

d) What is the value of c) ?

Answer: 1

4) What is the value of sum after the execution of the following code?

	sum = 0
	for counter in range(1, 5):
		sum = sum + 2 * counter

5) What is the output of the following code fragment (mySentence and partial are both strings)?

	mySentence = "It was a dark and stormy night"
	partial = mySentence[10:13]
	print partial	

Answer: ark

• a)

           #Program Error1
           number = raw_input("Please enter a number: ")
           number = number/2.0
           print number
           
   Answer: raw_input( ) is used to input a number.  It should be input( )
  

  
  

• b)

          #Program Error2
          response = raw_input("Do you like chocolate? ")
          if response == "yes":
              print "Me too!"
          	else:
              	print "That's too bad."
           
  Answer: else should be indented by the same amount as if
  

  
  

• c)

           #Program Error3
           secret = "csci110"
           response = raw_input("Enter the password: ")
           if response = secret:
           	print "Access granted."
           else:
           	print "Access denied.   
           
  Answer: The = in the conditional should be ==
  

  
  

• d)

           #Program Error4
           count = 0
           while count < 10
           	print count
           	count = count + 1
           
  Answer: The colon after the header of the while loop is missing.
  

7)  Consider the following while loop:
	sum = 0
	count = 5
	while count <= 10:
		sum = sum + count
		count = count + 1

a) Fill in the following table for the values of count and sum each time through the loop (there may be more rows than you need in the table):

b)Write a for loop that does the equivalent of the above loop.

sum = 0
for count in range(5, 11):
    sum = sum + count

  8. Consider the following Python code:

        sum = 0
        for i in range(1, 5):
              sum = sum + i
        print sum

Answer: 10

  9. Fill in the necessary code to fill in the depositList array with deposit amounts entered by the user. You should keep track of the sum of all the deposits made, so that the print statement at the end of the program makes sense. You can assume there are exactly 1000 deposits made.

Program deposit.py
sum = 0
depositList = [ ]

for i in range(1000):
    deposit = input("Please enter amount of deposit: ")
    depositList.append(deposit)
    sum = sum + deposit
    
print "The sum of the deposits: $%6.2f"% sum