Rounding is done in two main ways. 1. Decimal Places 2. Significant Figures

A question might tell you to round a number to 2dp, or 2 decimal places. This means that they want the answer to have __ digits after the decimal place. 3dp = __ digits 12dp = __ digits etc…

Step 1:Draw a line after the number of decimal places you want. e.g.Round to 3dp to 1dp to 4dp to 2dp

Step 2:If the next number after the line is low (0, 1, 2, 3, 4) then ignore everything after the line. e.g.Round to 3dp  to 1dp  to 4dp to 2dp

Step 3:If the next number after the line is high (5, 6, 7, 8, 9) then add one to the number to the LEFT of the line e.g.Round to 3dp to 1dp to 4dp  to 2dp 

Instead of a number of decimal places you can count every digit in the number except any zeros at the start or end of the number. When you round to significant figures you draw your line after that many digits. It is written as sf rather than dp

e.g.Round to 4sf 1929 to 3sf to 2sf to 3sf to 4sf to 1sf