Informally: as soon as you multiply an integer (a “whole” number, positive, an unfavorable or zero) time itself, the resulting product is dubbed a square number, or a perfect square or simply “a square.” So, 0, 1, 4, 9, 16, 25, 36, 49, 64, 81, 100, 121, 144, and also so on, are all square numbers.

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More formally: A square number is a variety of the type *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 reality that these certain numbers that objects have the right to be i ordered it to to fill a perfect square.

Children deserve to experiment v pennies (or square tiles) to check out what numbers of them deserve to be i ordered it in a perfectly square array.

Four pennies can:

Nine pennies can:

And sixteen pennies can, too:

But seven pennies or twelve pennies cannot be arranged that way. Numbers (of objects) that deserve to be arranged into a square variety are called “square numbers.

Square arrays must be full if we are to counting the number together a square number. Here, 12 pennies room arranged in a square, yet not a full square array, for this reason 12 is no a square number.

The number 12 is no a square number.

Children may enjoy exploring what number of pennies can be arranged into an open square choose this. They room not referred to as “square numbers” yet do follow an interesting pattern.

Squares do of square tiles are also fun come make. The number of square tiles that fit right into a square array is a “square number.”

**Here are two boards, ****3 × 3 and 5 × 5****. How numerous red tiles in each? Black? Yellow? Are any kind of of those square numbers?What if you brick a 4 × 4**

**or 6 × 6****plank the same way?Can friend predict the number of tiles in a 7 × 7****or 10 × 10****board?****Square number in the multiplication table**

Square numbers show up along the diagonal line of a standard multiplication table.

### Connections v triangular numbers

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

If you count the white triangles that are in the “spaces” in between the green ones, the sequence of number starts through 0 (because the first design has actually no gaps) and then continues: 1, 3, 6, 10, 15, …, again triangle numbers!Remarkably, if you count all the small triangles in each design—both green and white—the numbers room square numbers!

### A connection between square and triangular numbers, seen an additional way

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

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

. This square is the same size as 16 white rods i ordered it in a square. The number 16 is a square number, “4 squared,” the square the the length of the longest rod (as measured with white rods).Here’s an additional example:

. When inserted together, these make a square who area is 64, again the square that the size (in white rods) that the longest rod. (The brown rod is 8 white rods long, and also 64 is 8 time 8, or “8 squared.”)### Stair procedures from square numbers

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

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

Here space two examples. Color is used here to assist you check out what is gift described. Children enjoy color, yet don’t need it, and can often see an innovative ways of relenten stair-step trends that castle have constructed with single-color tiles. Or castle might shade on 1″ graph document to record their stair-step pattern, and show just how they interpreted it into a number sentence.A diamond-shape make from pennies can also be explained by the 1 + 2 + 3 + 4 + 5 + 4 + 3 + 2 + 1 = 25 number sentence.### From one square number to the next: two pictures with Cuisenaire rods

**(1)** begin with W. Add two continuous rods, W+R; then another 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)** start with W. Because that each new square, add two rods that enhance the political parties of the previous square, and also a new W to to fill the corner.