The method of rounding to a significant figure is often used as it can be applied to any kind of number, regardless of how big or small it is. When a newspaper reports a lottery winner has won £3 million, this has been rounded to one significant figure. It rounds to the most important figure in the number.
To round to a significant figure:
Round 53,879 to 1 significant figure, then 2 significant figures.
Notice that the number of significant figures in the question is the maximum number of non-zero digits in your answer.
Round 0.005089 to 1 significant figures, then 2 significant figures.
What is 98,347 rounded to 1 significant figure, and 2 significant figures?
What is 3.5175 rounded to 1 significant figure, and 2 significant figures?