Data types (int, double, String, bool) in Flutter - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an integer variable named count with value 10.

Flutter

int count = [1];

Drag options to blanks, or click blank then click option'

A"10"

B10.0

C10

Dtrue

Attempts:

3 left

💡 Hint

Common Mistakes

Using quotes around the number, which makes it a String.

Using a decimal number like 10.0 which is a double.

The variable count is declared as an integer, so the value must be a whole number without quotes.

2fill in blank

medium

Complete the code to declare a double variable named price with value 9.99.

Flutter

double price = [1];

Drag options to blanks, or click blank then click option'

A9.99

Btrue

C"9.99"

D9

Attempts:

3 left

💡 Hint

Common Mistakes

Using an integer value like 9 instead of 9.99.

Putting the number inside quotes, making it a String.

The variable price is a double, so the value must be a number with a decimal point without quotes.

3fill in blank

hard

Fix the error in the code by completing the declaration of a String variable named greeting with value Hello.

Flutter

String greeting = [1];

Drag options to blanks, or click blank then click option'

Atrue

B"Hello"

CHello

D9

Attempts:

3 left

💡 Hint

Common Mistakes

Not using quotes around the text.

Using single quotes inconsistently (though Dart allows single quotes, this example expects double quotes).

Strings must be enclosed in double quotes in Dart to be valid text values.

4fill in blank

hard

Fill both blanks to declare a boolean variable named isActive set to true.

Flutter

bool isActive = [1];

Drag options to blanks, or click blank then click option'

A"true"

B"false"

Cfalse

Dtrue

Attempts:

3 left

💡 Hint

Common Mistakes

Using quotes around true or false, which makes them Strings.

Using the wrong boolean value.

Boolean variables hold true or false without quotes.

5fill in blank

hard

Fill all three blanks to declare variables: an int age 25, a double height 1.75, and a String name "Alice".

Flutter

int age = [1];
double height = [2];
String name = [3];

Drag options to blanks, or click blank then click option'

A25

B1.75

C"Alice"

Dtrue

Attempts:

3 left

💡 Hint

Common Mistakes

Putting numbers inside quotes.

Using wrong types for the values.

Each variable must have the correct type and value format: int without quotes, double with decimal without quotes, and String with quotes.

Practice

1. Which data type in Flutter is used to store true or false values?

easy

A. bool

B. int

C. String

D. double

Solution

1. Step 1: Understand the bool data type

   The bool data type stores only two values: true or false.

2. Step 2: Compare with other data types

   int stores whole numbers, double stores decimals, and String stores text, so they do not fit true/false values.

3. Final Answer:

   bool -> Option A

4. Quick Check:

   bool = true or false [OK]

Hint: Remember: bool means true or false only [OK]

Common Mistakes:

• Confusing bool with int
• Thinking String can store true/false
• Using double for true/false

2. Which of the following is the correct way to declare a double variable named price with value 9.99 in Flutter?

easy

A. double price = 9,99;

B. double price = 9.99;

C. int price = 9.99;

D. String price = 9.99;

Solution

1. Step 1: Check the syntax for double declaration

   In Flutter, double values use a dot (.) as decimal separator, so 9.99 is correct.

2. Step 2: Verify variable type and value match

   double price = 9.99; is correct. double price = 9,99; uses comma which is invalid. int price = 9.99; uses int for decimal value. String price = 9.99; uses String but value is numeric.

3. Final Answer:

   double price = 9.99; -> Option B

4. Quick Check:

   double uses dot for decimals [OK]

Hint: Use dot (.) for decimals in double, not comma [OK]

Common Mistakes:

• Using comma instead of dot
• Assigning decimal to int
• Assigning number to String without quotes

3. What will be the output of this Flutter code?

int a = 5;
double b = 2.0;
print(a + b);

medium

A. 7.0

B. 7.00

C. 7

D. Error

Solution

1. Step 1: Understand type promotion in addition

   Adding int and double results in a double value in Flutter.

2. Step 2: Calculate the sum

   5 + 2.0 = 7.0 as a double, so print outputs 7.0.

3. Final Answer:

   7.0 -> Option A

4. Quick Check:

   int + double = double [OK]

Hint: int + double results in double output [OK]

Common Mistakes:

• Expecting int output
• Thinking print shows 7.00
• Assuming syntax error

4. Identify the error in this Flutter code snippet:

bool isActive = "true";

medium

A. Variable name is invalid

B. Missing semicolon

C. bool cannot store text in quotes

D. No error, code is correct

Solution

1. Step 1: Check bool assignment rules

   bool variables must be assigned true or false without quotes.

2. Step 2: Analyze the code

   "true" is a String, not a bool, so this causes a type error.

3. Final Answer:

   bool cannot store text in quotes -> Option C

4. Quick Check:

   bool = true or false without quotes [OK]

Hint: Assign bool without quotes, quotes mean String [OK]

Common Mistakes:

• Using quotes around true/false
• Ignoring type mismatch errors
• Assuming variable name causes error

5. You want to store a user's age, height in meters, name, and whether they are a student. Which Flutter data types should you use for age, height, name, and isStudent respectively?

hard

A. bool, String, double, int

B. double, int, bool, String

C. String, double, int, bool

D. int, double, String, bool

Solution

1. Step 1: Match each variable to its data type

   Age is a whole number -> int; height is decimal -> double; name is text -> String; isStudent is true/false -> bool.

2. Step 2: Verify option matches all types correctly

   int, double, String, bool matches int, double, String, bool in order for age, height, name, isStudent.

3. Final Answer:

   int, double, String, bool -> Option D

4. Quick Check:

   Whole number, decimal, text, true/false [OK]

Hint: Match data type to real-world meaning: number, decimal, text, true/false [OK]

Common Mistakes:

• Mixing int and double
• Using bool for text
• Confusing order of types