First, we have to know the rules to recognize significant numbers:
Zeros between two non-zero digits ARE significant.
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All non-zero numbers are significant.
Trailing zeros to the right of the decimal are significant.
Leading zeros are not significant.
Trailing zeros in a whole number with the decimal shown are significant.
Trailing zeros in a whole number with no decimal shown are not significant.
After these rules, we can say that 890 has only 2 significant numbers.
Answer: 2 significant digits
