Data types (int, double, String, bool) in Flutter - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

What will this Flutter Text widget display?

Consider this Flutter code snippet:

int count = 5;
double price = 3.5;
String label = 'Total';
bool isActive = true;

Text('$label: \$${count * price} - Active: $isActive')

What text will appear on the screen?

Flutter

int count = 5;
double price = 3.5;
String label = 'Total';
bool isActive = true;

Text('$label: \$${count * price} - Active: $isActive')

A Total: 17.5 - Active: false

B Total: 17.5 - Active: true

C Total: $17.5 - Active: true

D Total: $17.5 - Active: false

💡 Hint

Remember that \$ inside a string escapes the dollar sign to show it literally.

The string uses \$ to show the dollar sign literally, then ${count * price} calculates 5 * 3.5 = 17.5. The bool isActive is true, so the full text is 'Total: $17.5 - Active: true'.

📝 Syntax

intermediate

Which option correctly declares a double variable in Dart?

You want to store a decimal number in a variable named price. Which declaration is correct?

A double price = 9.99;

B int price = 9.99;

C String price = 9.99;

D bool price = 9.99;

💡 Hint

Decimals need a type that supports fractional numbers.

double is the correct type for decimal numbers. int only stores whole numbers. String stores text. bool stores true/false.

🧠 Conceptual

advanced

What is the result of this Dart expression?

Given:

int a = 3;
double b = 2.0;
bool c = (a > b);

What is the value of c?

Flutter

int a = 3;
double b = 2.0;
bool c = (a > b);

A 3.0

B true

C TypeError

D false

💡 Hint

Compare 3 and 2.0 using > operator.

3 is greater than 2.0, so (a > b) is true. The bool c stores true.

🔧 Debug

advanced

Why does this Dart code cause an error?

Look at this code:

int x = 5;
String y = x + 3;

Why does it cause an error?

Flutter

int x = 5;
String y = x + 3;

A You cannot assign int to String without conversion.

B Variables must be declared with var keyword.

C You cannot add int to int and assign to String directly.

D The + operator is not defined for int types.

💡 Hint

Check the types on both sides of the assignment.

x + 3 is an int (5 + 3 = 8). You cannot assign an int directly to a String variable without converting it to a string.

❓ lifecycle

expert

What happens if you try to change a final int variable in Flutter?

Consider this code:

final int count = 10;
count = 15;

What will happen when you run this code?

Flutter

final int count = 10;
count = 15;

A The value of count changes to 15 at runtime.

B No error, count becomes 15.

C Runtime error: Variable 'count' is immutable.

D Compile-time error: Cannot assign to final variable 'count'.

💡 Hint

final variables cannot be reassigned after initialization.

final means the variable can only be set once. Trying to assign a new value causes a compile-time error.