How many sig figs in 0.85?

two. Here are some rules for determining sigfigs:

1. Digits from 1-9 are always significant.
2. Zeros between two other significant figures are always significant
3. One or more additional zeros to the right of both the decimal place and another significant figure are significant.
4. Zeros used solely for spacing the decimal point (placeholders) are not significant.

eg.

NUMBER SIG FIGS EXPLANATION453 kg3All non-zero digits are always significant.5057 L4Zeros between 2 sigfigs are significant.5.003Additional zeros to the right of decimal and a sigfigs are significant.0.0071Placeholders are not significant