Rounding to significant figures is easy! Just count the number of places from the most significant figure- that is the digit with the largest place value. It is always the first digit from the left that is not a zero. If the next figure is 5 or more round it up. If the next figure is less than 5 delete the rest of the number. You may need to replace the figures with zeros as the numbers must keep their place value.
ExamplesRound 543 to 1 significant figure.
The most significant figure is 5 because it is in the hundreds column. The 4 means we don't have to round up. We replace the 43 with 00 because the 5 still means 5 hundred. 543 = 500 to 1 s.f.
Round 5.888 to 2 significant figures.
The two most significant figures are the 5 units and 8 tenths. The next figure is also an 8, which is more than 5 so we have to round up. The 8 tenths will become 9 tenths. The rest of the number is after the decimal point, so we do not have to replace it with zeros.
5.888 = 5.9 to 2 s.f.
Round 0.07695 to 3 significant figures.
Don't count 0's at the beginning, as they have no value. We call these 0's "placeholders" because they keep the other digits in the correct column. The most significant figure is the 7 hundredths, then the 6 thousandths and then the 9 ten thousandths. The next figure is a 5 so we have to round up the 9. When the 9 rounds up it becomes 10, so we add one to the thousandths column.
0.07695 = 0.0770 to 3 s.f. The zero at the end is important. It shows the number has been rounded to 3 s.f. Writing 0.077 would be wrong as this is only 2 s.f.
See if you can complete the table.
If you are getting some wrong find more help on
BBC Bitesize
then have another go.