1. Adding & Subtracting in Scientific Notation
Exponents are SAME
1.) If exponents same, add or subtract the coefficients and keep the power of 10.
Examples: (3.5 x 105) (8.9 x 10-3)
+ (2.3 x 105) (6.3 x 10-3)
5.8 x x 10-3
2.) If needed, adjust decimal and exponent so answer is in scientific notation.

2. Adding & Subtracting in Scientific Notation
Exponents are DIFFERENT
1.) If exponents different, change to the largest exponent.
Example:
(3.5 x 106) + (2.3 x 105)
0.23 x 106
2.) Add or subtract coefficients and keep the common base. (3.5 x 106)
+ (0.23 x 106)
3.73 x 106
3.) If needed, adjust decimal and exponent so answer is in scientific notation.
Change the term with smaller exponent to match the larger exponent.
Exponent increased.
Decimal decreased.

3. p. 54 in MSG
Example:
(9.21 x 108) + (8.2 x 108)

4. Change the term with smaller exponent to match the larger exponent.
p. 54 in MSG
Example:
(5 x 105) - (4.1 x 102)
Change the term with smaller exponent to match the larger exponent.

5. Change the term with smaller exponent to match the larger exponent.
p. 54 in MSG
Example:
(7.1 x 10-3) - (2.5 x 10-4)
Change the term with smaller exponent to match the larger exponent.

6. Change the term with smaller exponent to match the larger exponent.
p. 54 in MSG
Example:
(3.3) + (9.9 x 103)
Change the term with smaller exponent to match the larger exponent.