Rounding

Rounding is done in two main ways.

1. Decimal Places

2. Significant Figures

Decimal Places

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 = __ digits12dp = __ digits etc…

2312

How to round

Step 1: Draw a line after the number of decimal places you want.

e.g. Round 5.378245 to 3dp23.222756 to 1dp12.735691 to 4dp200.11658 to 2dp

How to round

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 5.378245 to 3dp 5.37823.222756 to 1dp 23.212.735691 to 4dp200.11658 to 2dp

How to round

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 5.378245 to 3dp23.222756 to 1dp12.735691 to 4dp 12.7357200.11658 to 2dp 200.12

Significant Figures

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. Round253.5283 to 4sf1929 to 3sf12.84582 to 2sf0.0034767 to 3sf0.7561123 to 4sf0.00591987 to 1sf

253.5

193013

0.00348

0.75610.006