When a bright object os placed 10 cm away from a concave mirror, its real image is formed at a distance 40cm from the mirror. What is the focal lencgt of the mirror

given,

object distance (u)=10cm

image distance (v)=40cm

focul length (f)=??

mirror formula

1/v+1/u=1/f

=1/40+1/10=1/f

= 1/40+4/40 (by taking l.c.m)

= 5/40=1/20

or f=20

so the focal length of the mirror is 20cm

if the answer is correct please give thums up