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What is 1 + 3?
sig fig rules
all nonzero numbers are significant
(12 = 2 sf)
zeros in between nonzero numbers are significant
(1000.09 = 6 sf)
zeros before nonzero numbers are NOT significant - placeholders
(0000039 = 2sf; 0.0000039 = 2sf)
zeros after a nonzero number AND after a decimal are significant -- measured zeros
(0.00200 = 3 sf)
zeros after a nonzero number but before a decimal are undefined UNLESS there is a period after the zeros
(20 = undefined; 20. = 2sf)