2.17. Exercises

1. Evaluate the following numerical expressions in your head, then use the active code window to check your results:

   1. 5 ** 2

   2. 9 * 5

   3. 15 / 12

   4. 12 / 15

   5. 15 // 12

   6. 12 // 15

   7. 5 % 2

   8. 9 % 5

   9. 15 % 12

   10. 12 % 15

   11. 6 % 6

   12. 0 % 7

   print(5**2)

   1. 5 ** 2  = 25

   2. 9 * 5 = 45

   3. 15 / 12 = 1.25

   4. 12 / 15 = 0.8

   5. 15 // 12 = 1

   6. 12 // 15 = 0

   7. 5 % 2 = 1

   8. 9 % 5 = 4

   9. 15 % 12 = 3

   10. 12 % 15 = 12

   11. 6 % 6 = 0

   12. 0 % 7 = 0

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2. What is the order of the arithmetic operations in the following expression. Evaluate the expression by hand and then check your work.

   2 + (3 - 1) * 10 / 5 * (2 + 3)

3. Challenge: Many people keep time using a 24 hour clock (11 is 11am and 23 is 11pm, 0 is midnight). If it is currently 13 and you set your alarm to go off in 50 hours, it will be 15 (3pm). Write a Python program to solve the general version of the above problem. Ask the user for the time now (in hours), and then ask for the number of hours to wait for the alarm. Your program should output what the time will be on the clock when the alarm goes off.

   ## question 5 solution ## current_time_string = input("What is the current time (in hours)? ") waiting_time_string = input("How many hours do you have to wait? ") current_time_int = int(current_time_string) waiting_time_int = int(waiting_time_string) hours = current_time_int + waiting_time_int timeofday = hours % 24 print(timeofday)

4. It is possible to name the days 0 thru 6 where day 0 is Sunday and day 6 is Saturday. If you go on a wonderful holiday leaving on day number 3 (a Wednesday) and you return home after 10 nights you would return home on a Saturday (day 6). Write a general version of the program which asks for the starting day number, and the length of your stay, and it will tell you the number of day of the week you will return on.

5. Challenge: Take the sentence: All work and no play makes Jack a dull boy. Store each word in a separate variable, then print out the sentence on one line using print.

   ## question 7 solution ## word1 = "All" word2 = "work" word3 = "and" word4 = "no" word5 = "play" word6 = "makes" word7 = "Jack" word8 = "a" word9 = "dull" word10 = "boy." print(word1 + ' ' + word2 + ' ' + word3 + ' ' + word4 + ' ' + word5 + ' ' + word6 + ' ' + word7 + ' ' + word8 + ' ' + word9 + ' ' + word10)

6. Add parentheses to the expression 6 * 1 - 2 to change its value from 4 to -6.

   print(6 * 1 -2) ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertEqual('-6\n', self.getOutput(), 'Checking output.') myTests().main()

7. Challenge: The formula for computing the final amount if one is earning compound interest is given on Wikipedia as

   

   Write a Python program that assigns the principal amount of 10000 to variable P, assign to n the value 12, and assign to r the interest rate of 8% (0.08). Then have the program prompt the user for the number of years, t, that the money will be compounded for. Calculate and print the final amount after t years.

   P = 10000 n = 12 r = 0.08 t = ?? ==== from unittest.gui import TestCaseGui import re class myTests(TestCaseGui): def testOne(self): self.assertTrue(re.search(str(P * (1 + (r/n))**(n*t))[:5], self.getOutput()), 'Checking Answer.') myTests().main()

   ## question 9 solution ## P = 10000 n = 12 r = 0.08 t = int(input("Compound for how many years? ")) final = P * ( ((1 + (r/n)) ** (n * t)) ) print("The final amount after", t, "years is", final)

8. Write a program that will compute the area of a circle. Prompt the user to enter the radius and save it to avariable called radius. Print a nice message back to the user with the answer.

   pi = 3.14 ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def test_radius(self): self.assertIn("radius", self.getEditorText(), 'radius variable') self.assertIn(str(3.14*radius**2)[:4], self.getOutput(), 'Checking answer.') myTests().main()

9. Challenge: Write a program that will compute the area of a rectangle. Prompt the user to enter the width and height of the rectangle and store the values in variables called width and height. Print a nice message with the answer..

   ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertIn('width', self.getEditorText()) self.assertIn('height', self.getEditorText()) self.assertIn(str(width*height), self.getOutput(), 'Checking answer.') myTests().main()

   ## question 11 solution width = int(input("Width? ")) height = int(input("Height? ")) area = width * height print("The area of the rectangle is", area)

10. Write a program that will compute MPG for a car. Prompt the user to enter the number of miles driven and store it in a variable called miles and the number of gallons used stored in a variable gallons. Print a nice message with the answer.

    ==== from unittest.gui import TestCaseGui import re class myTests(TestCaseGui): def testOne(self): self.assertTrue(re.search(str(miles/gallons)[:5], self.getOutput()), 'Checking answer.') myTests().main()

11. Challenge: Write a program that will convert degrees celsius to degrees fahrenheit.

    ## question 13 solution ## deg_c = int(input("What is the temperature in Celsius? ")) # formula to convert C to F is: (degrees Celcius) times (9/5) plus (32) deg_f = deg_c * (9 / 5) + 32 print(deg_c, " degrees Celsius is", deg_f, " degrees Farenheit.")

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12. Ask the user for the temperature in Fahrenheit and store it in a variable call deg_f. Calculate the equivalent temperature in degrees Celsius and store it in deg_c. Output a message to the user giving the temperature in Celsius.

    ==== from unittest.gui import TestCaseGui class myTests(TestCaseGui): def testOne(self): self.assertIn('deg_f', self.getEditorText()) self.assertIn('deg_c', self.getEditorText()) ans = (deg_f - 32)*5/9 self.assertAlmostEqual(ans, deg_c) self.assertIn(str(ans)[:min(len(str(ans)), 5)], self.getOutput(), 'Checking answer.') myTests().main()

13. Piece together the code so that a user is asked for two numbers, and then the sum of those two numbers is printed out.

            num_one = input("Please enter your first number: ")
    ====
    num_two = input("Please enter your second number: ")
    ====
    sum_of_input = int(num_one) + int(num_two)
    ====
    print(sum_of_input)
            

14. Write a program that will convert gallons to liters. This program will also need to get input from a user to see how many gallons should be converted and the result should be printed to the user.

            user_gallons = input("How many gallons should be converted?: ")
    ====
    num_gallons = int(user_gallons)
    ====
    liters = num_gallons * 3.785
    ====
    print("Number of liters: " + str(liters))
            

15. Write a program that will convert tablespoons to teaspoons. This program will also need to get input from a user to see how many tablespoons should be converted and the result should be printed to the user.

            user_tablespoons = float(input("How many tablespoons should be converted?: "))
    ====
    teaspoons = user_tablespoons * 3
    ====
    print("Number of teaspoons: " + str(teaspoons))
            

2.17.1. Contributed Exercises

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