Question

How to simplify `(7.1times10^-7)(8.6times10^-5)` in scientific notation?

Answer 1

You multiply the numbers and add the 10-powers.

Explanation:

`=(7.1*8.6)*(10^(-7-5))`
`=61.06*10^-12`

But we need to have only one digit in front of the decimal point:
`=(6.106*10^1)*10^-12=6.106*10^(1-12)=6.106*10^-11`

And, since the original numbers had only two significant digits, we will round this to `6.1*10^-11`

Comment : I've placed brackets where they weren't technically necessary, but they may have added to the understanding of the steps we've taken.