<h3>To round to a significant figure:</h3>
- look at the first non-zero digit if rounding to one significant figure.
- look at the digit after the first non-zero digit if rounding to two significant figures.
- draw a vertical line after the place value digit that is required.
- look at the next digit.
Yes, because even though other trees produce more oxygen, the small trees will still produce some oxygen. On top of this there are more small trees than big trees, so even though they make less oxygen, in whole they end up making more when added together!