Adding and Subtracting Numbers in Scientific Notation

When adding or subtracting numbers in scientific notation, the exponents must be the same.

Adding/Subtracting when Exponents are THE SAME Step 1 - add/subtract the decimal Step 2 – Bring down the given exponent on the 10

Step 2 – Bring down exponent : Example 1 (2.56 X 103) + (6.964 X 103) Step 1 - Add: 2.56 + 6.964 = 9.524 Step 2 – Bring down exponent : 9.524 x 103

Step 2 – Bring down exponent: Example 2 (9.49 X 105) – (4.863 X 105) Step 1 - Subtract: 9.49 – 4.863 = 4.627 Step 2 – Bring down exponent: 4.627 x 105

The sum of 5.6 x 103 and 2.4 x 103 is A 8.0 x 103 B 8.0 x 106 C Answer: A

The exponents are the same, so add the coefficients. The sum of 5.6 x 103 and 2.4 x 103 is A 8.0 x 103 B 8.0 x 106 C 8.0 x 10-3 D 8.53 x 103 The exponents are the same, so add the coefficients. Answer: A

8.0 x 103 minus 2.0 x 103 is A 6.0 x 10-3 B 6.0 x 100 C 6.0 x 103 D 7.8 x 103 Answer: C

8.0 x 103 minus 2.0 x 103 is A 6.0 x 10-3 B 6.0 x 100 C 6.0 x 103 D 7.8 x 103 Answer: C

Adding/Subtracting when the Exponents are DIFFERENT When adding or subtracting numbers in scientific notation, the exponents must be the same. If they are different, you must move the decimal so that they will have the same exponent.

Moving the Decimal It does not matter which number you decide to move the decimal on, but remember that in the end both numbers have to have the same exponent on the 10.

Adding With Different Exponents (4.12 x 106) + (3.94 x 104) (412 x 104) + (3.94 x 104) 412 + 3.94 = 415.94 415.94 x 104 Express in proper form: 4.1594 x 106

Subtracting With Different Exponents (4.23 x 103) – (9.56 x 102) (42.3 x 102) – (9.56 x 102) 42.3 – 9.56 = 32.74 32.74 x 102 Express in proper form: 3.274 x 103

Example 3 (2.46 X 106) + (3.4 X 103) Step 1 – Rewrite with the same exponents 3.4 X 103  0.0034 X 103+3 New Problem: (2.46 X 106) + (0.0034 X 106) Step 2 – Add decimals 2.46 + 0.0034 = 2.4634 Step 3 – Bring Down Exponents 2.4634 X 106

Example 4 (5.762 X 103) – (2.65 X 10-1) Step 1 – Rewrite with the same exponents 2.65 X 10-1  0.000265 X 10(-1+4) New Problem : (5.762 X 103) – (0.000265 X 103) Step 2 – Subtract Decimals 5.762 – 0.000265 = 5.761735 Step 3 – Bring down decimals 5.761735 X 103

7.0 x 103 plus 2.0 x 102 is A 9.0 x 103 B 9.0 x 105 C 7.2 x 103 D 7.2 x 102 Answer: C

7.0 x 103 plus 2.0 x 102 is A 9.0 x 103 B 9.0 x 105 C 7.2 x 103 D 7.2 x 102 Answer: C

7.8 x 105 minus 3.5 x 104 is A 7.45 x 105 B 4.3 x 104 C 4.3 x 106 D 4.3 x 1010 Answer: A

7.8 x 105 minus 0.35 x 105 is A 7.45 x 105 B 4.3 x 104 C 4.3 x 106 D 4.3 x 1010 Answer: A

Adding and Subtracting… The important thing to remember about adding or subtracting is that the exponents must be the same! If the exponents are not the same then it is necessary to change one of the numbers so that both numbers have the same exponential value.