significant figure

This is the name given to each of the digits needed in a number in order to denote that number to the appropriate degree of accuracy.

Sometimes an answer given to a calculation doesn’t have to be accurate – an estimate is enough.

However, at other times it has to be more precise and we have to round off the number to a specific number of significant figures.

The first significant figure is the first digit which isn’t zero.

For example, 0.063 correct to 1 significant figure is 0.06.

When the answer to a calculation is too long, we can round it off to the nearest thousand or million. When this happens, we may have to add zeros to keep the place value.

The following numbers show this. They have been rounded off to a specific number of significant figures:

• 19 984 = 20 000 to 2 sig. fig.

• 124 670 = 125 000 to 3 sig. fig.

• 2 379 600 = 2 380 000 to 4 sig. fig.