Informally: as soon as you multiply an essence (a “whole” number, positive, an adverse or zero) times itself, the result product is called a square number, or a perfect square or just “a square.” So, 0, 1, 4, 9, 16, 25, 36, 49, 64, 81, 100, 121, 144, and also so on, room all square numbers.

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More formally: A square number is a variety of the form n × n or n2 wherein n is any type of integer.

Mathematical background

Objects i ordered it in a square array

The surname “square number” comes from the fact that these specific numbers that objects deserve to be i ordered it to to fill a perfect square.

Children have the right to experiment v pennies (or square tiles) to see what number of them deserve to be arranged in a perfectly square array.

Four pennies can: 

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Nine pennies can: 

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And 16 pennies can, too: 

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But 7 pennies or twelve pennies cannot be arranged that way. Number (of objects) that can be arranged into a square selection are called “square numbers.

Square arrays should be full if we room to counting the number as a square number. Here, 12 pennies room arranged in a square, however not a full square array, so 12 is not a square number.


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The number 12 is no a square number.


Children might enjoy experimenting what numbers of pennies have the right to be arranged right into an open up square like this. They room not dubbed “square numbers” but do follow an amazing pattern.

Squares made of square tiles are additionally fun to make. The number of square tiles that fit into a square array is a “square number.”


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Here are two boards, 3 × 3 and 5 × 5. How numerous red tiles in each? Black? Yellow?Are any of those square numbers?What if you tile a 4 × 4 or 6 × 6 plank the same way?Can friend predict the variety of tiles in a 7 × 7 or 10 × 10 board?

Square number in the multiplication table


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Square numbers appear along the diagonal line of a typical multiplication table.


Connections through triangular numbers

If you count the eco-friendly triangles in every of this designs, the sequence of numbers you watch is: 1, 3, 6, 10, 15, 21, …, a sequence called (appropriately enough) the triangle numbers.

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If you counting the white triangle that are in the “spaces” between the green ones, the succession of number starts v 0 (because the an initial design has actually no gaps) and then continues: 1, 3, 6, 10, 15, …, again triangular numbers!

Remarkably, if you counting all the tiny triangles in every design—both green and also white—the numbers space square numbers!

A connection in between square and also triangular numbers, seen one more way

Build a stair-step plan of Cuisenaire rods, to speak W, R, G. Then build the an extremely next stair-step: W, R, G, P.

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Each is “triangular” (if we overlook the stepwise edge). Put the 2 consecutive triangle together, and they do a square:

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. This square is the same size as 16 white rods arranged in a square. The number 16 is a square number, “4 squared,” the square the the length of the longest rod (as measured v white rods).

Here’s another example:

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. When inserted together, these make a square
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whose area is 64, again the square that the length (in white rods) that the longest rod. (The brown stick is 8 white rods long, and also 64 is 8 times 8, or “8 squared.”)

Stair measures from square numbers

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Stair procedures that walk up and then earlier down again, favor this, also contain a square variety of tiles. When the tiles are checkerboarded, as they space here, an enhancement sentence that describes the number of red tiles (10), the number of black tiles (6), and the total number of tiles (16) shows, again, the connection in between triangular numbers and square numbers: 10 + 6 = 16.

Inviting youngsters in class 2 (or also 1) to build stair-step patterns and also write number sentence that describe these trends is a nice method to give them exercise with descriptive number sentence and also becoming “friends” v square numbers.

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Here room two examples. Shade is used right here to assist you see what is gift described. Children enjoy color, yet don’t need it, and can often see creative ways of explicate stair-step patterns that castle have built with single-color tiles. Or lock might shade on 1″ graph record to document their stair-step pattern, and also show just how they interpreted it into a number sentence.
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A diamond-shape made from pennies can likewise be described by the 1 + 2 + 3 + 4 + 5 + 4 + 3 + 2 + 1 = 25 number sentence.

From one square number come the next: two images with Cuisenaire rods

(1) begin with W. Add two continually rods, W+R; then an additional two, R+G; climate G+P; then….

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1;add 1+2;add 2+3;add 3+4;add 4+5;add 5+6;add 6+7

(2) begin with W. For each new square, include two rods that complement the sides of the previous square, and a brand-new W to to fill the corner.