The base of a cone is a circle, r = 7cm Base area of a cone = \(\pi\)r\(^2\) Curve surface area of a cone = \(\pi\)l \(\pi\)r\(^2\) : \(\pi\)l = 1 : 4 \(\frac{\pi r^2}{\pi l}\) = \(\frac{1}{4}\) \(\frac{r}{l} = \frac{1}{4}\) \(\frac{7}{l} = \frac{1}{4}\) cross multiplying l = 4 x 7 = 28cm.