Without doing any calculation, find the numbers which are surely not perfect squares.
(i) 153                (ii) 257                (iii) 408                 (iv) 441

Explanation

To determine which of the given numbers are surely not perfect squares, we can analyze the unit digit of each number. The unit digit of a perfect square can only be one of the following: 0, 1, 4, 5, 6, 9. If a number has a unit digit that is not in this set, it cannot be a perfect square.

Let's analyze each number step by step:

### Step 1: Analyze the number 153
- The unit digit of 153 is **3**.
- Perfect squares can have unit digits of: 0, 1, 4, 5, 6, 9.
- Since **3** is not in this list, **153 is surely not a perfect square**.
...