Microscope converging lens problem

[FritoTaco]

Homework Statement

A microscope slide is placed in front of a converging lens with a focal length of 2.44 cm. The lens forms an image of the slide 12.9 cm from the slide.

a. How far is the lens from the slide if the image is real?

Homework Equations

1/f = 1/di + 1/do The real equation (but harder in my opinion to read) is 1/p + 1/q = 1/f

The Attempt at a Solution

I know that if the image is real, focal length is positive on a converging lens (negative focal length for a diverging lens). I plugged 2.44cm into f and 12.9 into di. The problem is, I need a common denominator in this;
1/2.44 = 1/12.9 + 1/do. I can't find a least common multiple for 12.9 and 2.44. I tried to switched centimeters into millimeters and got 129mm and 24.4mm. This doesn't work because there's still a decimal in di (24.4mm). I don't know where to go from here because I'm use to using whole numbers but not decimals.

 

[ehild]

2.44 and 12.9 are not integers. Use their product as common denominator.

 

[FritoTaco]

Hey, it helped me a lot, thank you! I solved the problem correctly.

 

[ehild]

Well done!