It depends upon how you got to the 12, for example:
28.6 - 16.6 = 12.0
Because each of the numbers that was used to get to the 12 had 3 significant figures, you should write the 12 with three significant figures also.
However:
29 - 17 = 12
In this case, each of the numbers that was used to get to 12 had only 2 significant figures, so use only 2 significant figures in the 12.
Only three significant digits are correct, because 5.0 contains no digit for hundredths, and such a digit would be required to give four significant digits in the answer. Because 7 + 5 equals exactly 12, a third significant digit is gained for the answer. Note in contrast that the sum of 7.68 and 0.50 would properly contain four significant digits.
To express 124.683 with one significant digit, we round it to the nearest ten. The first significant digit is '1' in the hundreds place, so we round 124.683 to 100.
To express 961 to one significant figure, you round it to the nearest significant digit. The first significant digit in 961 is 9, and since the next digit (6) is 5 or greater, you round up. Therefore, 961 rounded to one significant figure is 1000.
Four - zeros between significant digits are significant.
To one significant digit, 37.19 is 4x101. Writing it as 40 makes it unclear as to whether you have 1 significant digit or 2.
They all have 1 as the first digit.
12 has two significant figures. A significant figure is any non-zero digit or any embedded or trailing zero. Leading zeros are not significant.
Only three significant digits are correct, because 5.0 contains no digit for hundredths, and such a digit would be required to give four significant digits in the answer. Because 7 + 5 equals exactly 12, a third significant digit is gained for the answer. Note in contrast that the sum of 7.68 and 0.50 would properly contain four significant digits.
All digits are significant in this case. Any digit after a decimal point is a significant digit.
The first significant digit is the 5, which is in the ten-thousandth's position.
To express 124.683 with one significant digit, we round it to the nearest ten. The first significant digit is '1' in the hundreds place, so we round 124.683 to 100.
Zero is considered a significant digit when it is to the left or the right of the decimal point. It is also a significant digit when it follows a non-zero digit or when it is between two digits.
Four - zeros in-between significant digits are significant.
4 significant digits.
All four digits are significant.
All digit are significant except: leading zeros,in the case of integers, trailing zeros.All digit are significant except: leading zeros,in the case of integers, trailing zeros.All digit are significant except: leading zeros,in the case of integers, trailing zeros.All digit are significant except: leading zeros,in the case of integers, trailing zeros.
To express 961 to one significant figure, you round it to the nearest significant digit. The first significant digit in 961 is 9, and since the next digit (6) is 5 or greater, you round up. Therefore, 961 rounded to one significant figure is 1000.