Rounded to one significant figure it becomes 10
10 significant figures.
Round 12 to 1 significant figure is 10.
To 1 significant figure, it would be 8 x 10^3.
10
One.
10
10
It is 10
11.5
It depends to what degree of accuracy: 10.25 (2 Decimal Places) 10.3 (1 Decimal Place) 10 (0 Decimal Places) 10 (1 Significant Figure) I included 1 Significant Figure for your future reference. If the number was 11.245 then to 1 Significant figure would be 10 because 0 does not count as a figure and therefore the 1 in 11 would be the only FIGURE.
The number 27000000 expressed using 1 significant figure is 3 x 10^7.