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Question 7

Create a magic square using the numbers 2 – 10. What strategy would you use for this? Compare it with the magic squares made using 1 – 9.

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Solution

A magic square is a grid where numbers in each row, column, and main diagonal add up to the same total.

Step 1 — Finding the 1-9 Magic Square

We first need a magic square using numbers from 1 to 9. This is a standard 3x3 magic square. The numbers are 1, 2, 3, 4, 5, 6, 7, 8, 9. The middle number of this set is 5. This middle number usually goes in the center of the square. Let us write down the classic 1-9 magic square.

Diagram 1

The magic square for numbers 1 to 9 is: 8, 1, 6 3, 5, 7 4, 9, 2

Now, let us find the magic sum for this square. We can add numbers in any row, column, or diagonal. Let us add the numbers in the first row.

8+1+68 + 1 + 6

=9+6= 9 + 6

15\boxed{15}

So, the magic sum for the 1-9 square is 15.

Step 2 — Strategy for 2-10 Magic Square

We need to create a magic square using numbers from 2 to 10. These numbers are 2, 3, 4, 5, 6, 7, 8, 9, 10. Notice that each of these numbers is exactly 1 more than the numbers 1 to 9. For example, 2 is 1+11+1, 3 is 2+12+1, and so on. The simplest strategy is to use our 1-9 magic square. We will add 1 to every number in that magic square. This will give us a new magic square. It will use the numbers 2 to 10.

Step 3 — Creating the 2-10 Magic Square

Let us take each number from the 1-9 magic square. We will add 1 to each number.

Original 1-9 square: 8, 1, 6 3, 5, 7 4, 9, 2

Applying the strategy (adding 1 to each number): 8+1=98+1=9, 1+1=21+1=2, 6+1=76+1=7 3+1=43+1=4, 5+1=65+1=6, 7+1=87+1=8 4+1=54+1=5, 9+1=109+1=10, 2+1=32+1=3

The new magic square for numbers 2 to 10 is: 9, 2, 7 4, 6, 8 5, 10, 3

Let us find the magic sum for this new square. We can add numbers in any row, column, or diagonal. Let us add the numbers in the first row.

9+2+79 + 2 + 7

=11+7= 11 + 7

18\boxed{18}

So, the magic sum for the 2-10 square is 18.

Diagram 2

Step 4 — Comparison of Magic Squares

We have two magic squares now. One uses numbers 1 to 9. The other uses numbers 2 to 10.

Let us compare their features.

The magic sum for the 1-9 square is 15. The magic sum for the 2-10 square is 18. The new magic sum is 15+3=1815 + 3 = 18. This is because we added 1 to each of the three numbers in every row, column, and diagonal.

The structure of both squares is the same. The relative positions of the numbers are identical. For example, the center number in both squares is the middle number of their set. For 1-9, the center is 5. For 2-10, the center is 6. And 6 is 5+15+1. Every number in the 2-10 square is exactly 1 more than the corresponding number in the 1-9 square.

Answer

(i) Strategy: Start with the classic magic square using numbers 1 to 9, then add 1 to each number in that square. (ii) New Magic Square (2-10): 9, 2, 7 4, 6, 8 5, 10, 3 (iii) Comparison: The magic square for numbers 2-10 has a magic sum of 18. The magic square for numbers 1-9 has a magic sum of 15. The structure and relative positions of numbers are the same. Each number in the 2-10 square is 1 greater than the corresponding number in the 1-9 square.

More questions in FIO

Q1

Arrange the stick figure cutouts given at the end of the book or draw a height arrangement such that the sequence reads:

(a) 0, 1, 1, 2, 4, 1, 5

(b) 0, 0, 0, 0, 0, 0, 0

(c) 0, 1, 2, 3, 4, 5, 6

(d) 0, 1, 0, 1, 0, 1, 0

(e) 0, 1, 1, 1, 1, 1, 1

(f) 0, 0, 0, 3, 3, 3, 3

Q2

For each of the statements given below, think and identify if it is Always True, Only Sometimes True, or Never True. Share your reasoning.

(a) If a person says '0', then they are the tallest in the group.

(b) If a person is the tallest, then their number is '0'.

(c) The first person's number is '0'.

(d) If a person is not first or last in line (i.e., if they are standing somewhere in between), then they cannot say '0'.

(e) The person who calls out the largest number is the shortest.

(f) What is the largest number possible in a group of 8 people?

Q3

Using your understanding of the pictorial representation of odd and even numbers, find out the parity of the following sums:

(a) Sum of 2 even numbers and 2 odd numbers (e.g., even + even + odd + odd)

(b) Sum of 2 odd numbers and 3 even numbers

(c) Sum of 5 even numbers

(d) Sum of 8 odd numbers

Q4

Lakpa has an odd number of ₹1 coins, an odd number of ₹5 coins and an even number of ₹10 coins in his piggy bank. He calculated the total and got ₹205. Did he make a mistake? If he did, explain why. If he didn't, how many coins of each type could he have?

Q5

We know that:

(a) even + even = even

(b) odd + odd = even

(c) even + odd = odd

Similarly, find out the parity for the scenarios below:

(d) even - even = _________

(e) odd - odd = _________

(f) even - odd = _________

(g) odd - even = _________

Q6

How many different magic squares can be made using the numbers 1 – 9?

Q7

Create a magic square using the numbers 2 – 10. What strategy would you use for this? Compare it with the magic squares made using 1 – 9.

Q8

Take a magic square, and

(a) increase each number by 1

(b) double each number

In each case, is the resulting grid also a magic square? How do the magic sums change in each case?

Q9

What other operations can be performed on a magic square to yield another magic square?

Q10

Discuss ways of creating a magic square using any set of 9 consecutive numbers (like 2 – 10, 3 – 11, 9 – 17, etc.).

Q11

Using this generalised form, find a magic square if the centre number is 25.

Q12

What is the expression obtained by adding the 3 terms of any row, column or diagonal?

Q13

Write the result obtained by— (a) adding 1 to every term in the generalised form. (b) doubling every term in the generalised form

Q14

Create a magic square whose magic sum is 60.

Q15

Is it possible to get a magic square by filling nine non-consecutive numbers?

Q16

A light bulb is ON. Dorjee toggles its switch 77 times. Will the bulb be on or off? Why?

Q17

Liswini has a large old encyclopaedia. When she opened it, several loose pages fell out of it. She counted 50 sheets in total, each printed on both sides. Can the sum of the page numbers of the loose sheets be 6000? Why or why not?

Q18

Here is a 2 × 3 grid. For each row and column, the parity of the sum is written in the circle; 'e' for even and 'o' for odd. Fill the 6 boxes with 3 odd numbers ('o') and 3 even numbers ('e') to satisfy the parity of the row and column sums.

Q19

Make a 3 × 3 magic square with 0 as the magic sum. All numbers can not be zero. Use negative numbers, as needed.

Q20

Fill in the following blanks with 'odd' or 'even':

(a) Sum of an odd number of even numbers is ______

(b) Sum of an even number of odd numbers is ______

(c) Sum of an even number of even numbers is ______

(d) Sum of an odd number of odd numbers is ______

Q21

What is the parity of the sum of the numbers from 1 to 100?

Q22

Two consecutive numbers in the Virahāṅka sequence are 987 and 1597. What are the next 2 numbers in the sequence? What are the previous 2 numbers in the sequence?

Q23

Angaan wants to climb an 8-step staircase. His playful rule is that he can take either 1 step or 2 steps at a time. For example, one of his paths is 1, 2, 2, 1, 2. In how many different ways can he reach the top?

Q24

What is the parity of the 20th term of the Virahāṅka sequence?

Q25

Identify the statements that are true.

(a) The expression 4m14m - 1 always gives odd numbers. (b) All even numbers can be expressed as 6j46j - 4. (c) Both expressions 2p+12p + 1 and 2q12q - 1 describe all odd numbers. (d) The expression 2f+32f + 3 gives both even and odd numbers.

Q26

Solve this cryptarithm:

UT+TATAT\begin{array}{rcc} & \text{U} & \text{T} \\ + & \text{T} & \text{A} \\ \hline \text{T} & \text{A} & \text{T} \end{array}
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