# Using Logic & Strategy to Solve Puzzles

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• 0:02 Puzzles
• 0:56 Using Logic
• 2:41 Using Strategy
• 3:59 Example
• 4:32 Lesson Summary
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Lesson Transcript
Instructor: Yuanxin (Amy) Yang Alcocer

Amy has a master's degree in secondary education and has taught math at a public charter high school.

In this lesson, you'll learn what strategies you can use to help you solve logic puzzles and Sudoku puzzles. Learn how you can find your answers as well as eliminate the wrong answers.

## Puzzles

In this lesson, you'll learn some tips you can use to solve logic puzzles and Sudoku puzzles. Sudoku puzzles are number puzzles involving a 9 x 9 grid subdivided into nine 3 x 3 grids. Each sub-grid contains the numbers 1 through 9 each occurring just once. Each row and each column likewise contain the numbers 1 through 9 each occurring just once. To start, you are given a few numbers with which you can finish the puzzle with.

Logic puzzles describe an event giving you just a few clues with which you'll use your logical thinking to piece together what happened. The puzzle is usually a set of clue and the end goal is to correctly match sets of information and fill in the blanks. To solve logic puzzles, it helps to create a grid showing you all the components of the event, like the one shown here. More on how to use this grid in a second.

You then mark all the right answers with a dot and all the wrong answers with an x.

## Using Logic

To solve logic puzzles, you use logic, that is, reasoning based on truths.

For example, when working with a Sudoku puzzle, if you see that in your very first sub-grid, you already have a 1, 2, 3, 4, 6, 7, 8, and 9, then you know that the one empty square must be a 5, since each number from 1 to 9 must be listed in each sub-grid.

In this example, look at the top left sub-grid. You've figured out where 4, 8, and 3 are located (the other numbers were filled in for you), so 5 must belong in the last blank spot in order to complete the sub-grid. Also, if you look at the middle sub-grids, you'll notice you have a 1 in the second and third rows. This tells you that the first row must have a 1 somewhere. Since the 1s are located in the middle and right sub-grids, the missing 1 must be in the left sub-grid. There are only two options there: on either side of the 3. Since the very first column already has a 1 in the top sub-grid, this means that your 1 must be in the third column to the right of the 3.

When it comes to logic puzzles, you'll use similar logic when you are given clues. The grid can help you keep track of all the information. For example, say you are given the clue that tells you that Zetafish.com received more investments than Fred Frost's company.

This clue doesn't tell you who started Zetafish.com, but it does tell someone who did not start the website. Because the clue mentions Zetafish.com as receiving more than Fred Frost, you can safely say that Fred Frost is not the owner of Zetafish.com. So you can draw an x where the column for Zetafish.com meets the row for Fred Frost.

## Using Strategy

In addition to using logic, you may also need to use strategy to solve your puzzles. Strategy involves using a plan of action to accomplish your goal, in this case, solving your puzzle.

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