Grade 7Mathematics

Squares and Square Roots

Squares of numbers; perfect squares; finding square roots by factor and table methods.

📖 5 min read · 3 worked examples · 8 practice questions

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The lesson

Everyone, let's start by understanding what a square means in mathematics. A square is simply the product of a number multiplied by itself. We write this as n squared, or . For example, 4² means 4 × 4. Here is a handy table of perfect squares up to 100. Notice how each entry on the right is the number on the left multiplied by itself: 1→1, 2→4, 3→9, and so on, ending with 10→100. These perfect squares show up in everyday situations—like the area of a square garden whose side length is a whole number of meters. To recap: a square means a number times itself, we denote it with the superscript 2, and the table gives you quick reference for the first ten squares.

Our Kenyan context: areas of square plots. A plot that measures 10 meters by 10 meters forms a perfect square. To find its area we multiply the side length by itself: 10 m × 10 m = 100 m², which we can also write as 10². If a farmer tells us the plot is 144 m², we need the side length. Taking the square root, √144 = 12, tells us each side is 12 meters. Remembering: squaring a side gives the area, and taking the square root of an area gives the side length. This is the key idea we'll use for land measurements across Kenya.

Class, let's dive into the factor method for finding square roots. This is a powerful tool when the number can be broken down into small prime factors. First, remember the key step: we pair identical prime factors and then take one from each pair. That's why the bullet point says, "Pair identical prime factors, take one from each..." Let's see this in action with our example: (\sqrt{144}). We factor 144 into (2^{2} \times 3^{2}). Each prime appears twice, so we can pair them. Taking one factor from each pair gives us (2 \times 3 = 6). Therefore, (\sqrt{144} = 6). This works best for perfect squares or numbers with small, easy‑to‑find factors. Notice the shape here represents the grouping of factor pairs—think of each pair as a side of a square. When you multiply the sides, you get the original number back. Any questions before we move on? Remember, practice breaking numbers into prime factors, and the square root will reveal itself.

Everyone, let's explore how we can quickly find square roots using a simple table method. First, remember to memorise the squares of numbers 1 through 10. This little lookup table becomes our secret tool. For example, to find the square root of 81, locate 81 in the squares column – you'll see it lines up with 9, so √81 equals 9. If the number isn't on the list, like 50, we see it falls between 49 (7²) and 64 (8²). That tells us √50 is somewhere between 7 and 8, so we can estimate its value. Any questions so far? Feel free to share an example you'd like to try, and we'll work through it together.

Everyone, we've come to the end of our lesson on squares and square roots. First, a square is simply a number multiplied by itself. When the root of that number is an integer, we call it a perfect square, like 9 or 16, because their square roots are whole numbers. Next, we learned two ways to find square roots: the factor method, where we pair up prime factors, and the table method, which relies on memorised squares you might have practiced. Finally, remember that the square root tells us the side length of a square area. This is useful in real‑world situations, like figuring out the size of a garden plot when you know its area. Before we finish, think about how you could use these ideas in everyday life—maybe measuring a piece of land or designing a simple floor tiling pattern.

Worked examples

– Perfect Square

Let's dive into our worked example titled Worked Example 1 – Perfect Square. First, we need to find the square root of 196 using factorisation. We start by breaking 196 down into its prime factors. Notice here that 196 can be written as 2 squared times 7 squared, or 2² × 7². Taking the square root of each factor gives √196 = 2 × 7, which equals 14. √196 is 14. Great job following each step! Remember, factorising a perfect square lets us pull out each pair of identical factors, making the square root straightforward.

– Non‑Perfect Square Estimate

Class, let's dive into Worked Example 2 – estimating a non‑perfect square, specifically (\sqrt{50}). First, recall the perfect squares around 50: (7^2 = 49) and (8^2 = 64). Since 50 is just a bit larger than 49, its square root will be a little more than 7. We can get a quick decimal estimate using linear interpolation. The formula shown is (7 + \frac{50-49}{64-49}=7.07). This tells us (\sqrt{50}) is about 7.07. Notice how we used the distance from 49 to 50, divided by the distance between the squares 49 and 64, then added that fraction to 7. It's a simple way to get a reasonable approximation without a calculator. Any questions so far? If not, let's move on to the next example where we'll apply the same technique to a larger number.

– Real‑World Problem

Class, let's work through a real‑world problem about a Kenyan farmer's garden. First, we know the area of the square garden is 36 square metres. The formula for the area of a square is side squared, written as Area = side². To find the length of one side, we rearrange the formula: side = √Area. We take the square root of 36. The square root of 36 is 6, which means each side of the garden measures 6 metres. The farmer's garden is a 6 m by 6 m square, giving a total area of 36 m² as stated. Great job, everyone! Remember, when you know the area of a square, just take the square root to get the side length.

Practice questions

  • For Q1, think about which number can be written as n × n. Visualize a 6 × 6 grid—that's 36.
  • Q2 asks for the square root of 81. Since 9 × 9 equals 81, the answer is 9.
  • Q3 is a multiple‑answer question. Remember 25 is 5² and 49 is 7², so those are perfect squares.
  • Q4 asks which methods work for finding √144. Using a calculator works, factoring into prime factors (144 = 12²) helps, and estimating with nearby squares (12² = 144) is also valid.
  • We estimate √68 with the table method. We know 8² is 64 and 9² is 81, so √68 lies between 8 and 9.
  • Consider the square plot with each side 12 metres. The area of a square is side multiplied by side, so 12 m × 12 m equals 144 square metres.
  • Finally, a farmer knows the plot area is 81 m² and wants the length of each side. Since the shape is a square, we need the square root of 81, which is 9 metres.
  • Great job, everyone! We've practiced finding square roots by factoring, estimating with tables, and applying those ideas to real‑world area problems.

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