### Theory:

Vinay's teacher asked him to round off the decimal number $$3.458$$ to the nearest whole number. Vinay did it correctly, so his teacher appreciated him, and Vinay was informed to teach the same to his friends.

He explained the following steps to his friends to round off the decimal number to the nearest whole number.
To round a decimal:

1. First underline the digit that is to be rounded.

2. Observe the digit which is right of the underlined number, if it is more than or equal to $$5$$, add $$1$$ to the underlined number.

3. If it is less than $$5$$, then the underlined number remains the same.

4. After rounding off the number, ignore all the digits after underlined number.
Example:
Let us round off the decimal $$4.689$$ to the nearest whole number.

First underlined the digit is to rounded $$=$$ $\underset{¯}{4}.689$

Here, we can observe that the digit next to the underlined digit is $$6$$, which is greater than $$5$$. So, the underlined number will add to $$1$$.

Therefore, the nearest digit of the $$4.689$$ to the nearest whole number is $$5$$.