Finding the 49-Square Structure in a Geometric Sequence

Perfect Squares with Geometric Sequence Elements

Here is a series of structures made of squares whose side length is 1 cm.

Is it possible to have a structure in the series that has 49 squares? If so, what element of the series is it?

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Will there be a term with 49 squares? If so, at what position?
00:05 Let's count the squares in each term
00:29 We see that the number of squares equals the term's position in the sequence
00:38 Therefore we can conclude this is the sequence formula
00:47 We want to find if there is a term with 49 squares
00:52 We'll substitute in the formula and solve for N
00:55 When taking a square root there are always 2 solutions (positive and negative)
00:59 There is no negative position in a sequence, so the positive solution is correct
01:02 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Here is a series of structures made of squares whose side length is 1 cm.

Is it possible to have a structure in the series that has 49 squares? If so, what element of the series is it?

2

Step-by-step solution

To determine if it is possible to have a structure in the series with 49 squares, consider the sequence of numbers representing perfect squares: 1, 4, 9, 16, 25, 36, 49, etc. Here, each number represents the total number of 1 cm x 1 cm squares contained in an n×n n \times n square.

The number 49 is indeed a perfect square, since 49=72 49 = 7^2 . This means that a structure made up of 49 squares can indeed be represented as a 7×7 7 \times 7 square.

Therefore, it is possible to have a structure in the series that has 49 squares, and it corresponds to the 7th square in the sequence (since n=7 n = 7 ), and this matches answer choice Yes, 7 7 .

3

Final Answer

Yes, 7 7

Key Points to Remember

Essential concepts to master this topic
  • Perfect Squares: Each structure contains n2 n^2 unit squares forming pattern
  • Recognition: Check if 49 = 72 7^2 , so 7th element works
  • Verification: Count squares in 7×7 grid: 49 squares total ✓

Common Mistakes

Avoid these frequent errors
  • Confusing element position with square count
    Don't think the 49th element has 49 squares = wrong sequence understanding! The element number equals the side length, not the total squares. Always remember: the nth element is an n×n square with n2 n^2 total squares.

Practice Quiz

Test your knowledge with interactive questions

Look at the following set of numbers and determine if there is any property, if so, what is it?

\( 94,96,98,100,102,104 \)

FAQ

Everything you need to know about this question

How do I know if a number can form a square structure?

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Check if the number is a perfect square! Take its square root - if you get a whole number, then it can form a square. For example: 49=7 \sqrt{49} = 7 , so 49 squares make a 7×7 structure.

What does 'element 7' actually mean in this sequence?

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Element 7 means the 7th structure in the series, which is a 7×7 square containing 72=49 7^2 = 49 unit squares. The element number always equals the side length!

Could 50 squares form a structure in this series?

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No! Since 507.07 \sqrt{50} \approx 7.07 is not a whole number, 50 is not a perfect square. Only perfect square numbers can form complete square structures.

How do I find which element has a specific number of squares?

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Take the square root of the number of squares. If it's a whole number, that's your element position! For 49 squares: 49=7 \sqrt{49} = 7 , so it's the 7th element.

Why does the pattern use perfect squares?

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Because we're building square structures! An n×n square always contains exactly n2 n^2 unit squares. This creates the sequence: 1, 4, 9, 16, 25, 36, 49...

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