Try these without a calculator. on these, dont round. do convert final answers to scientific notation. do the odds first, then the evens if you need more practice.
1. (61 x 10⁻⁷) + (2.25 x 10⁻⁵) + (212.0 x 10⁻⁶) =2. ( ― 54 x 10⁻²⁰ ) + ( ― 2.18 x 10⁻¹⁸ ) =3. ( ― 21.46 x 10⁻¹⁷ ) ― ( ― 3,250 x 10⁻¹⁹ ) =

1)

2)

3)

Step-by-step explanation:

1) First you need to reorder the terms, to do a simple sum:

  (61 x 10⁻⁷) + (2.25 x 10⁻⁵) + (212.0 x 10⁻⁶) =

Now you can simply sum each term, because the exponential is the same:

2) First you need to reorder the terms, to do a simple sum:

  ( ― 54 x 10⁻²⁰ ) + ( ― 2.18 x 10⁻¹⁸ ) =

Now you can simply sum each term, because the exponential is the same:

3) First you need to reorder the terms, to do a simple sum:

 ( ― 21.46 x 10⁻¹⁷ ) ― ( ― 3,250 x 10⁻¹⁹ ) =

Now you can simply sum each term, because the exponential is the same:

i believe the correct answer is b.

this is false ^.^ lol