Rounding to significant figures

Numbers which are significant are by and large any number which is not zero.

Zeros are usually said to be not significant, apart from two conditions:

  1. If the zero is the last digit after the decimal point
  2. If the zero is between two non-zero numbers

For example:

8300 has 2 significant figures

8030 has 3 significant figures

803 has 3 significant figures

80.3 has 3 significant figures

8.03 has 3 significant figures

0.803 has 3 significant figures

803.0 has 4 significant figures

0.8030 has 4 significant figures

Question

Round 5246 to 2 significant figures.

The first two significant figures are 5 and 2. As the next digit is 4 the 2 stays as it is.

Therefore 5246 rounds to 5200 to 2 significant figures. (Notice that we must put in zeros to keep the number starting with five thousand.)