All of those digits are significant.
It is 2215, exactly as in the question.
% rate= 2215/8430 * 100%= 0.2628 * 100%= 26.28%
37.753 rounded to one significant figure becomes 40
6276 as a significant figure would be 4 significant figures.
1000 is written with one significant figure, with only the 1 being a significant figure.
It has 1 significant figure.
The first significant figure of 0.000169 is the 1 and it has 3 significant figures.
The significant figure 2.00 has to do with the certainty of a measurement.
654 rounded to one significant figure becomes 700.
The significant figure of 78.00100 is 78.00. It had 7 significant figures and a least significant decimal of -5.
0.3 has one significant figure.
Rounded to 1 significant figure it is 0.4