An onion skin cell measures 0.04 mm. Under a microscope, it appears 103 larger. How large does the cell appear under the microscope?

0.4 mm

4 mm

40 mm

400 mm

I think you have a tiny typo: 103 is not likely?

if you meant 100 then

we need to multiply the original number by 100:

0.04*100=4, so it would appear as if it had 4 mm!

and if you meant 10 (if they typo was supposed to be 10x for example)

then we need to multiply by 10;

0.04*10=0.4 mm!