How far from a converging lens with a focal length of 15 cm should an object be placed to produce a real image which is half the size of the object?

Question

How do you solve this?

Thanks!

Answer 1

M = -1/2 = - di/do
di = 1/2 do
then
1/15 = 1/(0.5 do) + 1/do = 3/do
do/3 = 15/1
do = 45 cm

Old Science Guy gave you this.