Variables and Data Types — Intro to Programming Practice Worksheet

Grades 9–12 Easy difficulty 10 problems

A variable stores a value in memory and has a name. Assignment uses = in most languages (x = 5). Variables can be reassigned — the old value is replaced.

Common data types: integers (whole numbers), floats (decimals), strings (text in quotes), booleans (True/False). The type determines what operations are valid — you cannot divide a string by a number.

Declaring variables before use is required in some languages (Java, C++) but not in Python. Choose meaningful names (student_count not x) for readable code.

Skills practiced

  • Declaring and assigning variables
  • Identifying data types
  • Predicting output of simple assignments
  • Choosing appropriate types for data
Name: Date: Period:

Practice Worksheet: Variables and Data Types

Instructions: Solve each problem carefully. Show all work clearly. Write your final answer in the space provided or on a separate sheet as directed.

  1. 1.**Multiple Choice:** Which of the following is a valid variable name in Python?
    1. A. 2ndPlace
    2. B. my-variable
    3. C. my_variable
    4. D. class
  2. 2.**Short Answer:** What data type would you use to store a person's age? Explain why.
  3. 3.**Multiple Choice:** Which of the following is an example of a floating-point number?
    1. A. 42
    2. B. "3.14"
    3. C. 3.14
    4. D. True
  4. 4.**Free Response:** Write a line of Python code that creates a variable named score and assigns it the integer value 95.
  5. 5.**Short Answer:** What is the difference between the data types int and float?
  6. 6.**Multiple Choice:** Which of the following is NOT a basic data type in most programming languages?
    1. A. Integer
    2. B. String
    3. C. Loop
    4. D. Boolean
  7. 7.**Free Response:** Declare a variable called greeting that stores the text "Hello, World!".
  8. 8.**Short Answer:** What value does the expression 7 + 3.0 produce, and what is its data type?
  9. 9.**Multiple Choice:** Which of these is a Boolean value?
    1. A. 0
    2. B. "False"
    3. C. false
    4. D. False
  10. 10.**Free Response:** Explain why the following variable name is invalid in most programming languages: 2fast. Then, suggest a valid alternative.

Answer Key

  1. 1.
    my_variable is valid because it starts with a letter/underscore and contains only letters, digits, and underscores. 2ndPlace starts with a digit, my-variable contains a hyphen, and class is a reserved keyword.
    Final answer: C
  2. 2.
    Age is typically a whole number (e.g., 15, 21), so an integer data type is appropriate. It does not require decimal precision.
    Final answer: Integer (int)
  3. 3.
    3.14 is a floating-point number because it has a decimal point. 42 is an integer, "3.14" is a string, and True is a Boolean.
    Final answer: C
  4. 4.
    Final answer: score = 95
  5. 5.
    Final answer: An int (integer) stores whole numbers without a decimal point (e.g., 5, -3). A float (floating-point) stores numbers with a decimal point (e.g., 5.0, -3.14).
  6. 6.
    Loop is a control structure, not a data type. Integer, string, and Boolean are all basic data types.
    Final answer: C
  7. 7.
    Final answer: greeting = "Hello, World!"
  8. 8.
    The expression 7 + 3.0 produces 10.0, which is a float because adding an integer and a float results in a float.
    Final answer: 10.0, float
  9. 9.
    False is a Boolean value in Python (capitalized). false (lowercase) is not recognized as a Boolean in Python.
    Final answer: D
  10. 10.
    Final answer: The name 2fast is invalid because it starts with a digit. Most languages require variable names to begin with a letter or underscore. A valid alternative could be fast2 or twoFast.
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Common mistakes to avoid

  • Using = for comparison instead of assignment context
  • Confusing string "5" with integer 5
  • Forgetting quotes for string literals
  • Using reserved words as variable names

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