I dont understand..., HELP PLEASE

Question

I have an exam tomorrow, and my review sheet has this question that i dont understand:

 

Determine the difference of the expression (4.3*10⁸)-(3.8*10³). Show your work or justify your reasoning.

Answer 1

Difference means subtract.  But before you can subtract, you have to have your 10s to the same power.  Mark showed you two ways to do it.  

 

A third way might be,,,,

 

4.3*10⁸= 430000000

 

3.8 * 10³=3800

 

430000000 - 3800 = ?

 

Any of these methods work.  But you really need to learn the way Mark showed you.  What if the 10 was raised to the 97th power.  You wouldn't want to write all those zeros out! 

Answer 2

4.3 * 10⁸ - 3.8 * 10³

The numbers must be converted to the same power of 10.

430000 * 10³ - 3.8 * 10³ ⇒ (430000 - 3.8) * 10³ 

Or

4.3 * 10⁸ - 0.000038 * 10⁸ ⇒ (4.3 - 0.000038) * 10⁸