How many significant digits are in each number?
To figure out how many significant digits a number has, you must exclude all the leading zeroes, but include all the trailing ones. This is because you can re-write all numbers without leading zeroes, but the following ones presumably indicate extra accuracy. So 1.420 has four significant digits, because the trailing zero counts, but 0.010 has only two, becuse the trailing zero counts, but none of the leading zeroes. Likewise with the extreme case of 15,000,000… if it had just been written out as ‘fifteen million’, you’d assume only two significant digits, but since they put it in this numerical format you have no choice but to assume they mean EXACTLY fifteen million, so that’s EIGHT significant digits (you can’t start ignoring the rules because it’s a really big number!). It’s not too hard, so I’ll let you take it from there for the rest of your questions. Good luck!
