Optics, calculating image distance,.given magnification and focal length

[faria123]

Homework Statement

The image obtained with a converging lens is upright and 3x the length of the object. The focal length of the lens is 20cm. Calculate the object and image distances

Homework Equations

I have absolutely no idea how to even start this question

The Attempt at a Solution

1/object + 1/image = 1/focal (lens equation )
1/ob + 1/im= 1/20

M = ob/im ( magnification formula)
3= ob/im

I tried solving for each variable but it wasnt working...

 

[ehild]

Homework Statement

The image obtained with a converging lens is upright and 3x the length of the object. The focal length of the lens is 20cm. Calculate the object and image distances

Homework Equations

I have absolutely no idea how to even start this question

The Attempt at a Solution

1/object + 1/image = 1/focal (lens equation )
1/ob + 1/im= 1/20

M = ob/im ( magnification formula)
3= ob/im

I tried solving for each variable but it wasnt working...

Hi Faria, welcome to PF.

The magnification formula is wrong, look it after. And then show your work in detail.

Is the image real or virtual if the image is upright?

ehild