the circumference of a circle is 17.27 inches. what is the radius?

@ MAB25MAB: If 17.27 were the diameter, your answer would be correct.

However, Circumference is pi * the diameter, not twice the radius. 

$${\mathtt{C}} = {\mathtt{\pi}}{\mathtt{\,\times\,}}{\mathtt{d}}$$

Substitute in 17.27 for C:

$${\mathtt{17.27}} = {\mathtt{\pi}}{\mathtt{\,\times\,}}{\mathtt{d}}$$

$${\frac{{\mathtt{17.27}}}{{\mathtt{\pi}}}} = {\mathtt{d}}$$

$${\frac{{\mathtt{17.27}}}{{\mathtt{\pi}}}} = {\mathtt{5.497\: \!211\: \!734\: \!394\: \!064\: \!9}}$$

d = 5.497

Radius is half of the diameter:

$${\mathtt{r}} = {\frac{{\mathtt{d}}}{{\mathtt{2}}}}$$

$${\mathtt{r}} = {\frac{{\mathtt{5.497}}}{{\mathtt{2}}}} \Rightarrow {\mathtt{r}} = {\mathtt{2.748\: \!5}}$$

The radius is approximately 2.75 inches.

17.27/2=8.635