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Summary - Loops

Combine for, while and for-in to write a multiplication table.

Summary - Loops

In this group you learned for, while, do-while, for-in and break/continue. Now we will combine them to print a multiplication table.

The multiplication table is built by counting 1 to 5 with a for loop and writing 2 x i = (2*i) on each line. This structure combines repeated computation with formatted output.

Plan

We will build the multiplication table step by step: (1) count 1 to 5 with for (var i = 1; i <= 5; i++); (2) on each iteration write a line with print("2 x $i = ${2 * i}");; (3) interpolation embeds both i and 2 * i.

This structure is the skeleton of a real calendar or report app too. The loop + interpolation combo is the base of programs that produce screen output. Changing the number lets you build the 3-times or 4-times table easily.

Practice Multiplication table

Build a for (var i = 1; i <= 5; i++) loop. In the body print each line with print("2 x $i = ${2 * i}");. The output must be 5 lines: 2 x 1 = 2, 2 x 2 = 4, 2 x 3 = 6, 2 x 4 = 8, 2 x 5 = 10 (one product per line).

Starter code

main.dart
// Print the 2-times table with a for loop

Sample solution

main.dart
for (var i = 1; i <= 5; i++) {
  print("2 x $i = ${2 * i}");
}

Expected output

2 x 1 = 2
2 x 2 = 4
2 x 3 = 6
2 x 4 = 8
2 x 5 = 10

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 Which loop best fits the 2-times table (1-5)?

main.dart
// multiplication table
  • while
  • for Correct answer
  • do-while
  • if

Explanation: for is the best fit for a counted range.

2 Complete the for header

Question 
for (____) {
  print("2 x $i = ${2 * i}");
}
Answer 
for (var i = 1; i <= 5; i++) {
  print("2 x $i = ${2 * i}");
}

Explanation: The for header counting 1 to 5 is complete.

All lessons in Beginner

1 Dart basics

  1. What is Dart?
  2. Your first program
  3. dart run
  4. Comments
  5. String interpolation
  6. Summary - Dart basics

2 Variables

  1. var and type
  2. final
  3. const
  4. late
  5. Null safety
  6. Summary - Variables

3 Data types

  1. Integer types
  2. Floating-point types
  3. bool and String
  4. Type inference
  5. dynamic
  6. Summary - Data types

4 Project: Calculator

  1. Project design
  2. Add and subtract
  3. Multiply and divide
  4. Error handling
  5. Putting it together

5 Operators

  1. Arithmetic operators
  2. Assignment operators
  3. Comparison operators
  4. Logical operators
  5. Null-aware operators
  6. Summary - Operators

6 Strings

  1. Creating strings
  2. String interpolation
  3. length and methods
  4. substring
  5. contains and indexOf
  6. Summary - Strings

7 Conditionals

  1. The if statement
  2. else and else if
  3. switch
  4. Pattern matching
  5. Ternary
  6. Summary - Conditionals

8 Loops

  1. The for loop
  2. The while loop
  3. The do-while loop
  4. for-in
  5. break and continue
  6. Summary - Loops

9 Project: Shopping cart

  1. Cart design
  2. Adding items
  3. Calculating totals
  4. Listing the cart
  5. Putting it together

10 Lists

  1. Creating lists
  2. List access
  3. add and remove
  4. length and contains
  5. List methods
  6. Summary - Lists

11 Sets and Maps

  1. Set
  2. Set operations
  3. Map
  4. Map operations
  5. Map iteration
  6. Summary - Sets and Maps

12 Functions

  1. Defining functions
  2. Return values
  3. Arrow functions
  4. Optional parameters
  5. First-class functions
  6. Summary - Functions

13 Null safety in depth

  1. Nullable types
  2. Null-aware operators
  3. The ! operator
  4. late
  5. Null check
  6. Summary - Null safety

14 Class basics

  1. class
  2. Constructor
  3. Instance variables
  4. Methods
  5. this
  6. Summary - Class basics

15 Project: To-do CLI

  1. Task model
  2. Adding tasks
  3. Listing tasks
  4. Completing tasks
  5. Putting it together

16 Advanced string operations

  1. split and join
  2. replace
  3. trim and pad
  4. RegExp
  5. StringBuffer
  6. Summary - Advanced strings

17 Enums

  1. Defining enums
  2. Enum values
  3. Enhanced enums
  4. switch with enum
  5. Enum and patterns
  6. Summary - Enums

18 Exceptions

  1. try/catch
  2. throw
  3. finally
  4. The Exception class
  5. on clause
  6. Summary - Exceptions

19 Async basics

  1. Future
  2. async/await
  3. then
  4. Future.error
  5. Future.wait
  6. Summary - Async basics

20 Beginner final

  1. Project design
  2. Classes
  3. Collections
  4. Error handling
  5. Putting it together