NCERT Solutions • Class 7 Mathematics (Ganita Prakash) |
Solving questions with the help ofGanita Prakash Class 7 Solutionsand Class 7 Maths Chapter 6 Number Play NCERT Solutions Question Answer improves confidence.
NCERT Class 7 Maths Chapter 6 Number Play Solutions Question Answer
Ganita Prakash Class 7 Chapter 6 Solutions Number Play
NCERT Class 7 Maths Ganita Prakash Chapter 6 Number Play Solutions Question Answer
1 Numbers Tell Us Things
NCERT In-Text Questions (Pages 127-128)
What do the numbers in the figure below tell us?

Write down the number each child should say based on this rule for the arrangement shown below.
Solution:


Figure it Out (Page 128)
Question 1
|






Question 2
|
(b) Always True: If a person is the tallest, then no one is taller than them, so they will always say ‘0’. So, the given statement is always true.
(c) Always True: Each person is assigned a number that represents how many taller people are ahead of them. Since there is no one ahead of the first person, their number will always be ‘0’. Hence, the given statement is always true.
(d) Only Sometimes True: The statement is only sometimes true. A person standing in between can still be assigned ‘0’ if there are no taller people ahead of them.
(e) Only Sometimes True: The statement is only sometimes true. A person who calls out the largest number has many taller people in front but may not be the shortest overall. For example, if the shortest person is standing at the front, they will call out ‘0’. Meanwhile, the second shortest person could be at the back and might call out the largest number.
(f) If there are 8 people, then the shortest person will see 7 taller people. So the maximum number someone can say is 7.
2 Picking Parity
NCERT In-Text Questions (Pages 129-131)
Kishor has some number cards and is working on a puzzle: There are 5 boxes, and each box should contain exactly 1 number card. The numbers in the boxes should sum to 30. Can you help him fid a way to do it?

Can you figure out which 5 cards add to 30? Is it possible?
Explore what happens to the sum of (a) 4 odd numbers, (b) 5 odd numbers, and (c) 6 odd numbers.
Solution:
Based on the given examples for number cards 1, 3, 5, 7, 9, 11, 13.
(a) Sum of 4 odd numbers = 1 + 3 + 5 + 7 = 16 (even), can be arranged in pairs.
(b) Sum of 5 odd numbers = 1 + 3 + 5 + 7 + 9 = 25 (odd), cannot be arranged in pairs.
(c) Sum of 6 odd numbers = 1 + 3 + 5 + 7 + 9 + 11 = 36 (even), can be arranged in pairs.
Figure it Out (Page 131)
Question 1
|
(b) Odd + Odd = Even and Even + Even + Even = Even.
Adding the two results, we get Even + Even = Even.
The parity of the result is even.
Example: 3 + 5 + 2 + 4 + 6 = 8 + 12 = 20 (Even)
(c) Adding any 5 even numbers always gives an even number.
The parity of the result is even.
Example: 2 + 4 + 6 + 8 + 10 = 30 (Even)
(d) Odd + Odd = Even (4 such pairs).
Adding the 4 such results, we get
Even + Even + Even + Even = Even
The parity of the result is even.
Example: 1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 = 64 (Even)
Question 2
|
Question 3
|
(e) odd-odd
Example:
7 – 3 = 4 → even
9 – 5 = 4 → even
Parity of result = even
∴ odd – odd = even
(f) even-odd
Example:
8 – 3 = 5
12 – 5 = 7
Parity of result = odd
∴ even – odd = odd
(g) odd-even
Example:
7 – 2 = 5
9 – 6 = 3
Parity of result = odd
∴ odd – even = odd
Small Squares in Grids
NCERT In-Text Questions (Pages 131-132)
In a 3 × 3 grid, there are 9 small squares, which is an odd number. Meanwhile, in a 3 × 4 grid, there are 12 small squares, which is an even number.

Given the dimensions of a grid, can you tell the parity of the number of small squares without calculating the product?
Solution:
Yes, we can determine the parity of the number of small squares in a grid without directly calculating the full product, simply by observing the parity of the dimensions.
Rule: The product of two numbers is:
Find the parity of the number of small squares in these grids:
(a) 27 × 13
(b) 42 × 78
(c) 135 × 654
Solution:
(a) Both 27 and 13 are odd numbers, and Odd × Odd = Odd.
So, the parity of the number of small squares is odd.
(b) Both 42 and 78 are even numbers, and Even × Even = Even.
So, the parity of the number of small squares is even.
(c) 135 is odd, 654 is even, and Odd × Even = Even.
So, the parity of the number of small squares is even.
Parity of Expressions
NCERT In-Text Questions (Pages 132-133)
Consider the algebraic expression: 3n + 4.
For different values of n, the expression has different parity:

Come up with an expression that always has even parity.
Some examples are: 100p and 48w – 2. Try to find more.
Solution:
Expressions that have even parity are 2p + 10, 8n, 6m – 2, etc.
Come up with expressions that always have odd parity.
Solution:
Expressions that always have odd parity are 2m + 1, 8a + 3, etc.
Come up with other expressions, like 3n + 4, which could have either odd or even parity.
Solution:
Expressions, like 3n + 4, which could have either odd or even parity are: 5k – 2, n + 5, etc.
Are there expressions that we can use to list all the even numbers?
Hint: All even numbers have a factor of 2.
Solution:
All even numbers are multiples of 2, so to generate every even number, use 2n (where n = 1, 2, 3,…). This can list all the even numbers.
Are there expressions that we can use to list all odd numbers?
We saw earlier how to express the nth term of the sequence of multiples of 4, where n is the letter-number that denotes a position in the sequence (e.g., fist, twenty third, hundred and seventeenth, etc.).
Solution:
To list all odd numbers, we use 2n – 1 (where n = 1, 2, 3, ….).
This generates 1, 3, 5, 7, 9, …, capturing all odd numbers.
What would be the nth term for multiples of 2? Or, what is the nth even number?
Solution:
The nth term for multiples of 2 is 2n. The nth even number is also 2n.
3 Some Explorations in Grids
NCERT In-Text Questions (Pages 133-136)
Observe this 3 × 3 grid. It is filed following a simple rule— use numbers from 1 – 9 without repeating
any of them. There are circled numbers outside the grid.
Are you able to see what the circled numbers represent?
The numbers in the yellow circles are the sums of the corresponding rows and columns.
Fill the grids below based on the rule mentioned above:



Make a couple of questions like this on your own and challenge your peers.
Solution:
Do it yourself.
Can you find the other possible positions for 1 and 9?
Now, we have one full row or column of the magic square! Try completing it!
[Hint: First fill the row or columns containing 1 and 9]
Solution:


Figure it Out (Page 136)
Question 1
|

Question 2
|


Question 3
|



Question 4
|
Question 5
|


Generalising a 3 × 3 Magic Square
NCERT In-Text Questions (Pages 136-137)
We can describe how the numbers within the magic square are related to each other, i.e., the structure of the magic square.
Choose any magic square that you have made so far using consecutive numbers. If m is the letter-number of the number in the centre, express how other numbers are related to m, how much more or less than m.
[Hint: Remember how we described a 2 × 2 grid of a calendar month in the Algebraic Expressions chapter].
Solution:
Consider the magic square
We can express it using the letter-number m as:



Once the generalised form is obtained, share your observations with the class.
Solution:
Do it yourself.
Figure it Out (Page 137)
Question 1
|

Question 2
|
Question 3
|

Question 4
|

Question 5
|

The First-ever 4 × 4 Magic Square
NCERT In-Text Questions (Pages 137)
The first ever recorded 4 × 4 magic square is found in a 10th-century inscription at the Parshvanath Jain temple in Khajuraho, India, and is known as the Chautisa Yantra
The first ever recorded 4 × 4 magic square, the Chautlsa Yantra, at Khajuraho, India
Chautls means 34. Why do you think they called it the Chautisa Yantra?
Every row, column, and diagonal in this magic square adds up to 34.

Can you find other patterns of four numbers in the square that add up to 34?
Solution:
Yes, we can find different combinations of 4 numbers that add up 34 in the given square.
4 Nature’s Favourite Sequence: The Virahahka-Fibonacci Numbers!
Discovery of the Virahanka Numbers
NCERT In-Text Questions (Pages 141-142)
Use the systematic method to write down all 6-beat rhythms, i.e., write 6 as the sum of 1’s and 2’s in all possible ways. Did you get 13 ways?
Write a ‘1+’ in front of all rhythms having 5 beats and then a ‘2+’ in front of all rhythms having 4 beats. This gives us all the rhythms having 6 beats.
Yes, we get a total of 13 ways.

Write the next 3 numbers in the sequence:
1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ____, ____, ____, ……
If you have to write one more number in the sequence above, can you tell whether it will be an odd number or an even number (without adding the two previous numbers)?
Solution:
The next 3 terms in the sequence are:
55 + 89 = 144
89 + 144 = 233
144 + 233 = 377
To determine if the next number after 377 is odd or even without adding the previous terms, let’s examine the parity of the sequence.
Parity pattern: 1 (odd), 2 (even), 3 (odd), 5 (odd), 8 (even), 13 (odd), 21 (odd), 34 (even), 55 (odd), 89 (odd), 144 (even), 233 (odd), 377 (odd).
What is the parity of each term in the sequence? Do you notice any pattern in the sequence of parities?
Solution:
Here, the parity alternates as follows:
odd, odd, eve,n i.e., two odd numbers are followed by one even number.
So, the next number (after 377) will be even, as per the repeating parity cycle.
The pattern of parities: Repeats every 3 terms as Odd, Odd, Even.
5 Digits in Disguise
NCERT In-Text Questions (Pages 142-143)
Let us look at one more example shown on the right.
Here, K2 means that the number is a 2-digit number having the digit ‘2’ in the units place and ‘K’ in the tens place. K2 is added to itself to give a 3-digit sum HMM. What digit should the letter M correspond to?
Both the tens place and the units place of the sum have the same digit.
What about H? Can it be 2? Can it be 3?
M corresponds to 4 and H corresponds 144 to 1.
So, H cannot be 2 or 3.


These types of questions can be interesting and fun to solve! Here are some more questions like this for you to try out. Find out what each letter stands for.
Share how you thought about each question with your classmates; you may find some new approaches.
Solution:
YY is a 1 two-digit number where both digits are the same.
So it can be 99, 88,…..
But, Z is a 1-digit number and ZOO is a 1 3-digit number.
So, Y = 9, Z = 1, and O = 0.
Here, 5 + D = 5 ⇒ D = 0
Now, B + 3 = E0 ⇒ B = 7
If B = 7, then E = 1
So, we have B = 7, D = 0, and E = 1
Here, KP is a 2-digit number and PRR is a 3-digit number.
Basically, 2 × (KP) = PRR. So, P = 1.
If P = 1, then R = 2.
Hence, K = 6, P = 1, R = 2.
Here, C + 1 is a two-digit number i.e., 10.
So, C = 9 ⇒ F = 0





Figure it Out (Pages 143-144)
Question 1
|
Question 2
|
Question 3
|


We’ll track parities only (o or e), not actual numbers.
Row 1: A = o, B = e, C = e, then o + e + e = odd
Column 1 (A, D) = e means A must be paired with D to get the sum as even.
So, if A = o, D = o, then o + o = even
Similarly, if B = e, E = e, then e + e = even
Again, if C = e, F = o, then e + o = odd
So, the 6 boxes with 3 odd numbers and 3 even numbers are as follows:

Question 4
|
So, we will use the numbers (-4) to 4 to create a magic square whose magic sum is 0.

Question 5
|
Question 6
|

Question 7
|
Question 8
|


Question 9
|
Question 10
|
(b) Substituting j = 1 in 6j – 4 = 6 × 1 – 4 = 2 (even).
Substituting j = 2 in 6j – 4 = 6 × 2 – 4 = 8 (even).
This expression produces even numbers, but it does not produce all even numbers (for e.g., it skips 4 and 6).
This statement is false.
(c) Substituting p = 1, 2, 3,….. in 2p + 1, we get 3, 5, 7,…..
Substituting q = 1, 2, 3,…. in 2q + 1, we get 1, 3, 5, 7,…….
Here, 2q – 1 describes all the odd numbers but 2p + 1 does not describe 1.
Thus, this statement is false.
(d) Substituting f = 1, 2f + 3 = 2 × 1 + 3 = 5 (odd).
Substituting f = 2, 2f + 3 = 2 × 2 + 3 = 7 (odd).
The expression 2f + 3 always gives odd numbers because 2f is even and adding 3 makes it odd.
This statement is false.
Question 11
|


CBSE 2026-27 Board Exam Preparation & Practice Papers
Free Chapter Notes & Question Bank by BoardExams.in