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Lesson 1: Logic Puzzles

15-20 minutes

What You Will Learn

In this lesson, you will:

What Are Logic Puzzles?

Logic puzzles are brain challenges that you solve by thinking carefully -- not by guessing. They do not need math or special knowledge. You just need to pay attention, think step by step, and use clues to figure out the answer.

Logic puzzles use the same skills you have been learning in this course:

Let us try some together!

Puzzle 1: The River Crossing

The Farmer, the Fox, the Chicken, and the Grain

A farmer needs to cross a river with a fox, a chicken, and a bag of grain. The farmer has a small boat that can only carry the farmer and ONE other thing at a time.

Here is the problem:

  • If the farmer leaves the fox alone with the chicken, the fox will eat the chicken.
  • If the farmer leaves the chicken alone with the grain, the chicken will eat the grain.

How can the farmer get everything across the river safely?

Hints

  • Think about which two things can safely be left together. (The fox and the grain are fine together!)
  • The farmer might need to bring something BACK across the river at some point.
  • Try acting it out with toys or pieces of paper!
Solution:
  1. The farmer takes the chicken across. (The fox and grain are safe together.)
  2. The farmer goes back alone.
  3. The farmer takes the fox across.
  4. The farmer brings the chicken back. (So the fox does not eat it!)
  5. The farmer takes the grain across. (The fox and grain are safe together.)
  6. The farmer goes back alone.
  7. The farmer takes the chicken across.

Everyone is safely across! The trick was bringing the chicken back in step 4. Sometimes you have to go backwards to move forwards -- just like in debugging!

Puzzle 2: Truth Teller and Fibber

Two Guards, Two Doors

Imagine you are in a room with two doors. One door leads to a treasure. The other door leads to nothing.

There are two guards. One guard ALWAYS tells the truth. The other guard ALWAYS lies. You do not know which is which.

You can ask ONE question to ONE guard. What question should you ask to find the treasure door?

Let Us Simplify This

This is a tricky puzzle! Let us try an easier version first:

Imagine there are two people: Sam always tells the truth and Pat always lies.

  • If you ask Sam "Is the sky blue?" Sam says YES (truth).
  • If you ask Pat "Is the sky blue?" Pat says NO (lie).

Now, what if you asked one person about what the OTHER person would say? That is the key to the puzzle!

Solution:

Ask either guard: "If I asked the OTHER guard which door leads to the treasure, what would they say?"

Then choose the OPPOSITE door from what they tell you!

Why does this work?

  • If you ask the truth teller, they will honestly tell you what the liar would say -- which is the wrong door.
  • If you ask the liar, they will lie about what the truth teller would say -- which also gives you the wrong door.

Either way, you always get the wrong door as the answer. So pick the other one! This puzzle is about thinking two steps ahead -- just like in coding when you think about what your code will do step by step.

Puzzle 3: Grid Logic

Who Lives Where?

Three friends -- Alex, Bella, and Carlos -- each live in a different colored house: red, blue, or yellow. Use the clues to figure out who lives where!

Clues:

  1. Alex does NOT live in the red house.
  2. Bella does NOT live in the blue house.
  3. Carlos does NOT live in the yellow house.
  4. The person in the blue house is NOT Carlos.

Use this grid to help you solve it. Put an X for "no" and a checkmark for "yes":

Red Blue Yellow
Alex
Bella
Carlos
Solution:
  • From clue 1: Alex is NOT in the red house.
  • From clue 3: Carlos is NOT in the yellow house.
  • From clue 4: Carlos is NOT in the blue house.
  • So Carlos must be in the red house! (It is the only one left for him.)
  • From clue 2: Bella is NOT in the blue house. Since Carlos is in red, Bella must be in yellow.
  • That means Alex lives in the blue house!

Answer: Alex = Blue, Bella = Yellow, Carlos = Red

Grid logic puzzles are all about using clues to cross off what is NOT possible until you find what IS possible. This is exactly how computers make decisions -- by checking conditions one at a time!

Why Logic Puzzles Help Your Brain

Logic Puzzles and Coding Skills

Every time you solve a logic puzzle, you are using the same thinking skills that coders use:

  • Reading carefully -- like reading code to understand what it does
  • Working step by step -- like following a sequence of instructions
  • Checking your work -- like testing and debugging
  • Trying different approaches -- like iteration
  • Not giving up -- like persistence in problem-solving!

Key Takeaways

Ready for More?

Next Lesson

In Lesson 2, you will explore strategy games that make you a better thinker!

Start Lesson 2

Module Progress

You have finished Lesson 1! Your logic muscles are getting stronger.

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