Explanation:

Let's break down the pattern:

- The given pair is 5 : 36.

- Observing the numbers, 36 is 6 squared (6 × 6).

- 6 comes just after 5, so perhaps, the logic is: (number + 1)².

Let's check that:

- For 5: (5 + 1)² = 6² = 36

Now, for 7:

- (7 + 1)² = 8² = 64

Let's check the options:

- Option 1: 36 ? (Already paired with 5)

- Option 2: 49 ? (7², not fitting pattern)

- Option 3: 64 (Correct, as shown)

- Option 4: 81 ? (9², not matching)

Correct answer:

- Option 3: 64