Question

A virus measures 0.000022mm in length.
what value expresses the length of the virus in the scientific notation

Answer 1

how did you get that ?

Answer 2

Consider the number 500. Isn't this the same as saying 5*10*10? So we can express this as:\[5*10^2\]

So for every 10's place you go up or down a power of ten. So in this example, consider the digits as moving 10's places downwards.



So count every step down, and you'll see you're moving 5 decimal places to the right, giving you smaller and smaller numbers. So you know it's:
\[2.2*10^{-5}\]

Why do you stop there at 2.2 and not 0.22 or 22.0? Because scientific notation puts everything in terms of it's highest, single 1's digit with and that's just how it is.