Question

How can I add and subtract numbers written in scientific notation?

Answer 1

Best to write both numbers in standard notation if you can't use a calculator.

Let's add 4.723 x `10^6` and 8 x `10^4`

4723000
+80000

Write the numbers so that columns are matched up appropriate which would place the 8 directly under the 2.

This allows us to find an answer of 4803000 or 4.803 x `10^6`

If you need to worry about significant figures, you should report an answer of 4.80 x `10^6` because the rule for addition or subtraction is to keep the last full column - in this example that is the column with the 2 and the 8.

You can use the same trick for really small numbers, just make sure you line up the decimal points from both numbers.