does anyone know the rules for significant figures?

Answer 1

for multiplication and division your answer can have no more than the lowest number of sig figs given

for addition and subtraction no smaller place value than the biggest number

Zeroes don't count unless there's a decimal

so for multiply and divide 15 * 3 would be 50 because 15 has two but 3 only has one so instead of 45 it would go to 50 because 50 has one sig fig.

for adding and subtracting 3.5 + 4 = 8 because 3.5 has one after the decimal but 4 has none after the decimal
similarly 3500 + 420 = 3900 because 3500 goes to the hundreds and 420 goes to the tens

500 has one sig fig
500. has 3 sig figs

Answer 2

1Non-zero digits are always significant.
2Any zeros between two significant digits are significant.
3A final zero or trailing zeros in the decimal portion ONLY are significant.
Your answer must have the same number of significants as the smallest given.

Answer 3

In scientific measurement you cannot have an answer that has more significant figures than your least accurate measurement.

Answer 4

There are none