How to round a number off to 1 significant figure (1sf or 1 sig fig)

How To Round To 1 Significant Figure Video

Rounding to 1 significant figure is very useful when you need to estimate. Your 1st significant figure is the first number from the start of the number you need to round (ignoring any zeros at the start). Let’s take a look at a few examples:

Example 1:

Round 574.89 to 1 significant figure

First highlight your first significant figure:

574.89

Now since the number after 5 is 7 (which is 5 or above) you round the number up to 600.

Example 2:

Round 4193 to 1 significant figure.

Again, highlight your first significant figure.

4193

Now since the number after 4 is 1 (which is less than 5) you round the number down to 4000.

Example 3:

Round 31.586 to 1 significant figure.

Again, highlight your first significant figure.

31.586

Now since the number after 3 is 1 (which is less than 5) you round the number down to 30.

Example 4:

Round 6.497 to 1 significant figure.

Again, highlight your first significant figure.

6.497

Now since the number after 6 is 4 (which is less than 5) you round the number down to 6.

Example 5:

Round 394178.314 to 1 significant figure.

Again, highlight your first significant figure.

394178.314

Now since the number after 3 is 9 (which is 5 or above) you round the number up to 400000.

Example 6:

Round 0.003814 to 1 significant figure.

Again, highlight your first significant figure. Since the number is a small number, you ignore the zeros at the start of the number.

0.003814

Now since the number after 3 is 8 (which is 5 or above) you round the number up to 0.004 (don’t put 0’s after 0.003)

Example 7:

Estimate this calculation by rounding the numbers off to 1 significant figure.

482 × 12.781

Again all you need to do is round the number off to 1 significant figure.

482 = 500

12.781 = 10

So 500 × 10 is about 5000.

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