what is the area of a circle if the radius is 5cm to three significant figures?
+5478 The formula for area of a circle is: $${\mathtt{A}} = {\mathtt{\pi}}{\mathtt{\,\times\,}}{{\mathtt{r}}}^{{\mathtt{2}}}$$
Since the radius is 5, r2 = 25 and:
$${\mathtt{A}} = {\mathtt{\pi}}{\mathtt{\,\times\,}}{\mathtt{25}} \Rightarrow {\mathtt{A}} = {\mathtt{78.539\: \!816\: \!339\: \!744\: \!831}}$$
Rounded to 3 significant figures: 78.5 cm2
+5478 The formula for area of a circle is: $${\mathtt{A}} = {\mathtt{\pi}}{\mathtt{\,\times\,}}{{\mathtt{r}}}^{{\mathtt{2}}}$$
Since the radius is 5, r2 = 25 and:
$${\mathtt{A}} = {\mathtt{\pi}}{\mathtt{\,\times\,}}{\mathtt{25}} \Rightarrow {\mathtt{A}} = {\mathtt{78.539\: \!816\: \!339\: \!744\: \!831}}$$
Rounded to 3 significant figures: 78.5 cm2
