Rules for significant figures:

1. Leading Zeros: Zeros at the beginning of a number (0.00...) are never significant. They only indicate the position of the decimal point.
2. Captive Zeros: Zeros between non-zero digits are always significant (the '0' in 407).
3. Trailing Zeros: Zeros at the end of a number after a decimal point are significant (they indicate precision). Digits: 4, 0, 7, 0, 0 are significant. Total = 5.