How many significant figures are in 20.0?

Question

I know all non-zero digits are significant and any zero after the decimal point is significant, but I'm not sure if the zero in the ones place is significant. So would it be two or three?

Answer 1

Zeroes AFTER the decimal point is significant but zeroes in the ONES place isn't?

That doesn't make any sense to me at all.  I think you have that wrong.