This activity is all about significant figures.
Significant means important.
1 significant figure
In the number 4,725, the number 4 is the most significant. It has the value 4,000.
But 4,725 is closer to 5,000 than 4,000.
Following the normal rules of rounding, 4,725 becomes 5,000 when rounded to 1 significant figure. Rounding to 1 significant figure is the least accurate way of rounding.
2 significant figures
Rounding to 2 significant figures is more accurate. We now look at the second number, and round accordingly.
4,725 is closer to 4,700 than 4,800.
4,725 is 4,700 to 2 sig. figs.
3 significant figures
Rounding to 3 significant figures, we look at the third digit.
4,725 is closer to 4,730 than to 4,720. (Remember 5 rounds up)
4,725 rounds to 4,730 to 3 sig. figs.
It is a common mistake to say that 4,725 rounds to 5 to 1 sig. fig., instead of 5,000.
The zeros here are important to get the place values correct. They are important but not significant.
Let's try some questions now.