At what distance from a convex lens of focal length 30 cm an object should be placed, so that the size of image be 1/4^th of the object?

150 cm

Image is real

∴ m = $\frac{v}{m}=-\frac{1}{4}$  or  $v=-\frac{u}{4}$

As  $\frac{1}{v}-\frac{1}{u}=\frac{1}{f}$

∴ $\frac{1}{(-u / 4)}-\frac{1}{u}=\frac{1}{30}$

$-\frac{4}{u}-\frac{1}{u}=\frac{1}{30}$

or u = -150 cm