Question

How it is decided to where we put decimal point when we are writing a bigger number in standard form using exponents.

Answer 1

The number before the decimal will be a number less than 10.
for example if the number is 48000000
it can only be written as 4.8 x 10^7.
Not 48 x 10^6 or any other format.
If the number is 0.0000012
it can only be written as 1.2 x 10^(-6).