5 significant figures.
Rounded to two significant figures, 7.42 grams is approximately equal to 7.4 grams.
4 of them.
302.05 grams
5
5 significant figures.
There are 3 significant figures in '4.50g'
The 3 and the 2.
Rounded to two significant figures, 7.42 grams is approximately equal to 7.4 grams.
The significant figures are the ones which convey meaningful information about the measurement beyond the magnitude. Saying that a sample weighs .0000039 grams is better stated as 3.9 x 10^-6 grams or perhaps 3.9 micrograms. That's two significant figures. All the zeroes are not significant.
There are four significant figures in 33050. The trailing zero is not significant because there is no decimal. There would be five significant figures in 33050. If we were to remove the last zero in the number, we would alter the value of the number. Had the number been 3305.0, then there would have been four significant digits.
Three of them.
302.5 grams
302.05 grams
4 of them.
In the number 0.0023040, all the digits except for zero are considered significant. Zeros that are sandwiched between non-zero digits are also considered significant, so all the zeroes in this number are significant. Therefore, 0.0023040 grams has 7 significant figures, not 5.
There are 4 significant figures in this problem.