Question

Consider the following calendar.

In which of the following the difference between the product of diagonal number will be equal to 7

• A.
• B.
• C.
• D.

Answer 1

Answer: (A), (C)

The correct options are
A

C

Let us take the 4 number forming the square as

The difference of product of diagonal will be equal to

$28\times 22-21\times 29$

$616-609$

$7$

Let us take one more 4 number forming the square as

The difference of product of diagonal will be equal to

$19\times 13-12\times 20$

$247-240$

$7$

We observe that difference is 7 in both, hence we conclude that if we take any 4 numbers forming a square, the difference of product of diagonal will always be equal to 7

Now, Let us take the 9 number forming the square as

The difference of product of diagonal will be equal to

$15\times 3-1\times 17$

$45-17$

$28$

Let us take one more 9 number forming the square as

The difference of product of diagonal will be equal to

$28\times 16-14\times 30$

$448-420$

$28$

We observe that difference is 28 in both, hence we conclude that if we take any 9 numbers forming a square, the difference of product of diagonal will always be equal to 28