Question 4
Rewrite each sequence of Table 1 in your notebook, along with the next three numbers in each sequence! After each sequence, write in your own words what is the rule for forming the numbers in the sequence.

We will find the next three numbers for each sequence and describe the rule.
Step 1 — All 1's
This sequence has only the number 1. Every number in this sequence is the same.
The given sequence is 1, 1, 1, 1.
We need to find the next three numbers.
Step 2 — Counting numbers
This sequence lists numbers in order, starting from 1.
The given sequence is 1, 2, 3, 4, 5, 6, 7.
We add 1 to the previous number to get the next one.
Step 3 — Odd numbers
This sequence lists odd numbers in order, starting from 1.
The given sequence is 1, 3, 5, 7, 9, 11.
We add 2 to the previous number to get the next one.
Step 4 — Even numbers
This sequence lists even numbers in order, starting from 2.
The given sequence is 2, 4, 6, 8, 10, 12, 14.
We add 2 to the previous number to get the next one.
Step 5 — Triangular numbers
This sequence is formed by adding counting numbers.
The given sequence is 1, 3, 6, 10, 15, 21, 28.
We add the next counting number to the previous term. After adding 7 to get 28, we add 8, then 9, then 10.
Step 6 — Squares
This sequence is formed by multiplying a counting number by itself.
The given sequence is 1, 4, 9, 16, 25, 36, 49. These are , , , , , , .
We need to find the next three squares. These will be , , .
Step 7 — Cubes
This sequence is formed by multiplying a counting number by itself three times.
The given sequence is 1, 8, 27, 64, 125, 216. These are , , , , , .
We need to find the next three cubes. These will be , , .
Step 8 — Virahanka numbers
This sequence is also known as the Fibonacci sequence.
The given sequence is 1, 2, 3, 5, 8, 13, 21.
We add the two previous numbers to get the next one. For example, , , , and so on.
Step 9 — Powers of 2
This sequence is formed by multiplying the previous number by 2.
The given sequence is 1, 2, 4, 8, 16, 32, 64.
We multiply the last number by 2 to get the next one.
Step 10 — Powers of 3
This sequence is formed by multiplying the previous number by 3.
The given sequence is 1, 3, 9, 27, 81, 243, 729.
We multiply the last number by 3 to get the next one.
Answer
All 1's: 1, 1, 1, 1, 1, 1, 1. The next three numbers are 1, 1, 1. The rule is that every number is 1. Counting numbers: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. The next three numbers are 8, 9, 10. The rule is to add 1 to the previous number. Odd numbers: 1, 3, 5, 7, 9, 11, 13, 15, 17. The next three numbers are 13, 15, 17. The rule is to add 2 to the previous number. Even numbers: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20. The next three numbers are 16, 18, 20. The rule is to add 2 to the previous number. Triangular numbers: 1, 3, 6, 10, 15, 21, 28, 36, 45, 55. The next three numbers are 36, 45, 55. The rule is to add the next natural number in sequence. Squares: 1, 4, 9, 16, 25, 36, 49, 64, 81, 100. The next three numbers are 64, 81, 100. The rule is to square the next natural number. Cubes: 1, 8, 27, 64, 125, 216, 343, 512, 729. The next three numbers are 343, 512, 729. The rule is to cube the next natural number. Virahanka numbers: 1, 2, 3, 5, 8, 13, 21, 34, 55, 89. The next three numbers are 34, 55, 89. The rule is to add the last two numbers. Powers of 2: 1, 2, 4, 8, 16, 32, 64, 128, 256, 512. The next three numbers are 128, 256, 512. The rule is to multiply the last number by 2. Powers of 3: 1, 3, 9, 27, 81, 243, 729, 2187, 6561, 19683. The next three numbers are 2187, 6561, 19683. The rule is to multiply the last number by 3.
More questions in FIO
Can you think of other examples where mathematics helps us in our everyday lives?
How has mathematics helped propel humanity forward? (You might think of examples involving: carrying out scientific experiments; running our economy and democracy; building bridges, houses or other complex structures; making TVs, mobile phones, computers, bicycles, trains, cars, planes, calendars, clocks, etc.)
Can you recognise the pattern in each of the sequences in Table 1?
Rewrite each sequence of Table 1 in your notebook, along with the next three numbers in each sequence! After each sequence, write in your own words what is the rule for forming the numbers in the sequence.
Copy the pictorial representations of the number sequences in Table 2 in your notebook, and draw the next picture for each sequence!
Why are 1, 3, 6, 10, 15, ... called triangular numbers? Why are 1, 4, 9, 16, 25, ... called square numbers or squares? Why are 1, 8, 27, 64, 125, ... called cubes?
You will have noticed that 36 is both a triangular number and a square number! That is, 36 dots can be arranged perfectly both in a triangle and in a square. Make pictures in your notebook illustrating this!
This shows that the same number can be represented differently, and play different roles, depending on the context. Try representing some other numbers pictorially in different ways!
What would you call the following sequence of numbers?
That's right, they are called hexagonal numbers! Draw these in your notebook. What is the next number in the sequence?
Can you think of pictorial ways to visualise the sequence of Powers of 2? Powers of 3?
Can you find a similar pictorial explanation for why adding counting numbers up and down, i.e., 1, 1 + 2 + 1, 1 + 2 + 3 + 2 + 1, ..., gives square numbers?
By imagining a large version of your picture, or drawing it partially, as needed, can you see what will be the value of 1 + 2 + 3 + ... + 99 + 100 + 99 + ... + 3 + 2 + 1?
Which sequence do you get when you start to add the All 1's sequence up? What sequence do you get when you add the All 1's sequence up and down?
Which sequence do you get when you start to add the counting numbers up? Can you give a smaller pictorial explanation?
What happens when you add up pairs of consecutive triangular numbers? That is, take 1 + 3, 3 + 6, 6 + 10, 10 + 15, ... Which sequence do you get? Why? Can you explain it with a picture?
What happens when you start to add up powers of 2 starting with 1, i.e., take 1, 1 + 2, 1 + 2 + 4, 1 + 2 + 4 + 8, ... ? Now add 1 to each of these numbers—what numbers do you get? Why does this happen?
What happens when you multiply the triangular numbers by 6 and add 1? Which sequence do you get? Can you explain it with a picture?
What happens when you start to add up hexagonal numbers, i.e., take 1, 1 + 7, 1 + 7 + 19, 1 + 7 + 19 + 37, ... ? Which sequence do you get? Can you explain it using a picture of a cube?
Find your own patterns or relations in and among the sequences in Table 1. Can you explain why they happen with a picture or otherwise?
Can you recognise the pattern in each of the sequences in Table 3?
Try and redraw each sequence in Table 3 in your notebook. Can you draw the next shape in each sequence? Why or why not? After each sequence, describe in your own words what is the rule or pattern for forming the shapes in the sequence.
Count the number of sides in each shape in the sequence of Regular Polygons. Which number sequence do you get? What about the number of corners in each shape in the sequence of Regular Polygons? Do you get the same number sequence? Can you explain why this happens?
Count the number of lines in each shape in the sequence of Complete Graphs. Which number sequence do you get? Can you explain why?
How many little squares are there in each shape of the sequence of Stacked Squares? Which number sequence does this give? Can you explain why?
How many little triangles are there in each shape of the sequence of Stacked Triangles? Which number sequence does this give? Can you explain why? (Hint: In each shape in the sequence, how many triangles are there in each row?)
To get from one shape to the next shape in the Koch Snowflake sequence, one replaces each line segment '—' by a 'speed bump' _/_ . As one does this more and more times, the changes become tinier and tinier with very very small line segments. How many total line segments are there in each shape of the Koch Snowflake? What is the corresponding number sequence? (The answer is 3, 12, 48, ..., i.e., 3 times Powers of 4; this sequence is not shown in Table 1.)