Patterns in Mathematics | IT

Question 1

Why does this happen? Do you think it will happen forever?

Check your answer with HomiSolve it yourself, then let Homi check your steps and spot mistakes.
Solution

Adding up consecutive odd numbers always gives us a square number.

Step 1 — Finding the pattern

Let us look at the numbers. We add odd numbers one by one. The first odd number is 1. The sum is 1. This is 1×11 \times 1.

The first two odd numbers are 1 and 3. We add them together. The sum is 4. This is 2×22 \times 2.

The first three odd numbers are 1, 3, and 5. We add them together. The sum is 9. This is 3×33 \times 3.

The first four odd numbers are 1, 3, 5, 7. We add them together. The sum is 16. This is 4×44 \times 4.

We see a clear pattern here. The sum of NN odd numbers is N×NN \times N. We can write this as N2N^2.

Sum of N odd numbers=N2\boxed{\text{Sum of } N \text{ odd numbers} = N^2}

Diagram 1

Step 2 — Why this happens

Let us think about squares. A square has equal sides. We can draw squares using small blocks. Look at the diagram below.

The first odd number is 1. It makes a 1×11 \times 1 square. It uses 1 block.

The next odd number is 3. We add 3 blocks around the first square. This makes a 2×22 \times 2 square. It uses 1+3=41 + 3 = 4 blocks.

The next odd number is 5. We add 5 blocks around the 2×22 \times 2 square. This makes a 3×33 \times 3 square. It uses 4+5=94 + 5 = 9 blocks.

The next odd number is 7. We add 7 blocks around the 3×33 \times 3 square. This makes a 4×44 \times 4 square. It uses 9+7=169 + 7 = 16 blocks.

Each time, we add the next odd number. This new number always fits perfectly. It forms the next bigger square. The number of blocks added is always odd. We add blocks along two sides. We also add one corner block. So, the total is always odd. So, the sum of NN odd numbers is always N2N^2.

Diagram 2

Step 3 — Will it happen forever?

Yes, this pattern will happen forever. We can always make a bigger square. We just add the next odd number of blocks. Let us have an N×NN \times N square. We add 2N+12N + 1 blocks. This 2N+12N + 1 is always the next odd number. It will form a (N+1)×(N+1)(N+1) \times (N+1) square. So, this pattern never ends. It is a basic property of numbers.

Answer

(i) Each odd number added perfectly completes the next square. (ii) Yes, this pattern will happen forever. (iii) We always add the next odd number to form a new square.

More questions in IT

Q1

Why does this happen? Do you think it will happen forever?

Q2

How can we partition the dots in a square grid into odd numbers of dots: 1, 3, 5, 7,... ?

Q3

By drawing a similar picture, can you say what is the sum of the first 10 odd numbers?

Q4

Now by imagining a similar picture, or by drawing it partially, as needed, can you say what is the sum of the first 100 odd numbers?

Q5

Can you find a similar pictorial explanation?

← Back to Patterns in Mathematics