Question

In the following number-pairs, the second number is obtained by applying certain mathematical operations to the first number. Select the set in which the numbers are related in the same way as are the numbers of the following sets.

(NOTE: Operations should be performed on the whole numbers, without breaking down the numbers into its constituent digits. E.g. 13 - Operations on 13 such as adding/subtracting/multiplying etc. to 13 can be performed. Breaking down 13 into 1 and 3 and then performing mathematical operations on 1 and 3 is not allowed.)

10,99

21, 440

• A. 30, 899
• B. 3, 23
• C. 26, 298
• D. 15, 285

Answer 1

Answer:

A. 30, 899

We look for the rule:

Pair 1: (10 → 99)

Try:
$10^2 = 100,\quad 100 - 1 = 99$

So rule is:
$n \rightarrow n^2 - 1$

Check Pair 2: (21 → 440)

$21^2 = 441,\quad 441 - 1 = 440$

Rule matches.

Final Answer:

The relationship is:
$\boxed{n^2 - 1}$

(30,899)