An object is placed at 20 cm from a convex mirror of focal length 10 cm. The image formed by the mirror is : 

Virtual and at 20/3 cm from the mirror

Use : \(\frac{1}{f}\) = \(\frac{1}{v}\) + \(\frac{1}{u}\) 

Here $ u = -20cm , f = 10cm $

$\Rightarrow \frac{1}{v} = \frac{1}{10} - \frac{1}{-20} = \frac{1}{10} + \frac{1}{20} = \frac{3}{20}$

$\Rightarrow v = \frac{20}{3}$

v is positive hence image is virtual.