How to use scientific counting to express a score, for example, 1 / 200000? What about other scores?

How to use scientific counting to express a score, for example, 1 / 200000? What about other scores?

1/200000=1/2*1/100000=0.5*10＾（-5）=5*10＾（-6）
If you want to convert a fraction to a decimal, notice how many times 10 is negative,
Also, the number in front of the scientific counting method must be between 1 and 10
Please click the [select as satisfactory answer] button below,

The number expressed by scientific counting method is 2.01 × 10 to the negative 7th power, the original number is? The number expressed by scientific counting method is 5 × 10 to the negative 6th power, the original number is? The number expressed by scientific counting method is 3.02 × 10 to the negative 8th power, the original number is?

The negative power of multiplying by 10 is equal to the same positive power of dividing by 10, that is, the decimal point moves to the left idempotent, so the above three original digits are 0.00000021, 0.000005 and 0.0000000302

Should the results of physics calculation in college entrance examination be written in the form of score or scientific counting
For example, the result is 4 √ 3x10 to the power of - 2, but the answer is √ 3 / 25. These two numbers are the same. Which is better on the paper?

√3/25...