. A 8.0 cm high flower is placed 40 cm from a lens. The resulting image is 4.0 cm high and is inverted.

. A 8.0 cm high flower is placed 40 cm from a lens. The resulting image is 4.0 cm high and is inverted. Find the focal length of the lens

Please show formulas

Use the 2 formulas below.
Magnification = h’/h = s’/s
h’/h = height of image / height of object, s’/s = distance from mirror to image/ distance from mirror to object.
AND
1/f = 1/s + 1/s’

h = 8.cm, h’ = 4 cm, s = 40 cm
4/8 = s’/40, s’ = 20 cm
The image is 20 cm behind the lens.

1/f = 1/40 + 1/20 = 3/40
Focal length = 40/3 = 13⅓ cm