Question

How do you round 0.00222755 to four significant figures and express the result in scientific notation?

Answer 1

Let's do this one at a time

Explanation:

Significant figures
Start counting from the first non-zero. In this case the `7` is the fourth significant figure. Since this is followed by a `5` we will have to round up (0-4=down, 5-9=up).
`0.002228`

Scientific notation
Is of the form `axx10^b` where `a` is a number with just one non-zero digit in front of the decimal point. To get there, we have to move the decimal point 3 to the right. Thus 3 means an exponent of 3, to the right means it is negative:
`2.228xx10^-3`

You could also have done it this way:
`0.002228=2.228/1000=2.228/10^3=2.228xx10^-3`