Geometric Square Sequence: Finding the 46-Square Structure Pattern

Triangular Numbers with Pattern Recognition

The following is a series of structures formed by squares with side lengths of 1 cm.

Is it possible for a structure to have 46 squares? If so, which 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 46 squares? If so, at what position?
00:03 Let's count the squares in each term
00:25 We can see that the number of squares equals the term's position in the sequence
00:34 Therefore, we can conclude this is the sequence formula
00:40 We want to find if there is a term with 46 squares
00:45 Let's substitute into the formula and solve for N
00:50 Let's isolate N
00:53 The solution is not a whole number, therefore no such term exists
00:57 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

The following is a series of structures formed by squares with side lengths of 1 cm.

Is it possible for a structure to have 46 squares? If so, which element of the series is it?

2

Step-by-step solution

To determine whether a structure can have exactly 46 squares and identify which element of the series it corresponds to, we must first recognize the growth pattern of the series of squares in the diagram.

From examining patterns in geometric series, commonly encountered shapes include arrangements forming triangles or squares. Typically, triangular numbers are related to sums of consecutive integers:

The nn-th triangular number is given by:

Tn=n(n+1)2 T_n = \frac{n(n+1)}{2}

Let's calculate the first few triangular numbers to understand the sequence:

  • T1=1×(1+1)2=1 T_1 = \frac{1 \times (1+1)}{2} = 1
  • T2=2×(2+1)2=3 T_2 = \frac{2 \times (2+1)}{2} = 3
  • T3=3×(3+1)2=6 T_3 = \frac{3 \times (3+1)}{2} = 6
  • T4=4×(4+1)2=10 T_4 = \frac{4 \times (4+1)}{2} = 10
  • T5=5×(5+1)2=15 T_5 = \frac{5 \times (5+1)}{2} = 15
  • T6=6×(6+1)2=21 T_6 = \frac{6 \times (6+1)}{2} = 21
  • T7=7×(7+1)2=28 T_7 = \frac{7 \times (7+1)}{2} = 28
  • T8=8×(8+1)2=36 T_8 = \frac{8 \times (8+1)}{2} = 36
  • T9=9×(9+1)2=45 T_9 = \frac{9 \times (9+1)}{2} = 45
  • T10=10×(10+1)2=55 T_{10} = \frac{10 \times (10+1)}{2} = 55

Now, check if 46 is among these numbers, as this would indicate a structure with exactly that many squares.

Checking the sequence above, 4646 does not appear. 4545 is the highest number before 4646, and 5555 is the nearest higher one.

Since 4646 is not found in the series of triangular numbers, it is not possible for a structure in this series to have exactly 46 squares.

Therefore, the final answer is No.

3

Final Answer

No

Key Points to Remember

Essential concepts to master this topic
  • Formula: Triangular numbers follow T_n = n(n+1)/2 pattern
  • Technique: Calculate T_9 = 9×10/2 = 45, T_10 = 10×11/2 = 55
  • Check: Verify 46 falls between T_9 = 45 and T_10 = 55 ✓

Common Mistakes

Avoid these frequent errors
  • Assuming all positive integers appear in triangular sequences
    Don't assume every number like 46 must be triangular = wrong conclusions! Triangular numbers have gaps between them (like 45 to 55). Always calculate the sequence values systematically using the formula.

Practice Quiz

Test your knowledge with interactive questions

Is there a term-to-term rule for the sequence below?

18 , 22 , 26 , 30

FAQ

Everything you need to know about this question

What exactly are triangular numbers?

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Triangular numbers represent arrangements of objects in triangular patterns. The formula Tn=n(n+1)2 T_n = \frac{n(n+1)}{2} gives you the total number of objects in the nth triangular arrangement.

Why can't 46 squares form a triangular structure?

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Because 46 doesn't equal n(n+1)2 \frac{n(n+1)}{2} for any whole number n. The closest triangular numbers are 45 and 55, so 46 falls in the gap between them.

How do I know which triangular numbers to check?

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Start calculating from T_1 and work upward until you either find your target number or pass it. Since T_9 = 45 and T_10 = 55, we know 46 isn't triangular.

Could this be a different type of number sequence?

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The geometric pattern in the diagram shows triangular arrangements of squares. Other sequences like square numbers (1, 4, 9, 16...) follow different formulas and wouldn't match this visual pattern.

What if I made a calculation error?

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Double-check by substituting back: if n=9, then 9×102=45 \frac{9 \times 10}{2} = 45 . If n=10, then 10×112=55 \frac{10 \times 11}{2} = 55 . Since 45 < 46 < 55, we confirm 46 isn't triangular.

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