Round 39.2 to 1 significant figure Step by Step

Step by step

The question

Question: round 39.2 to 1 significant figure.

Round 39.2 to 1 significant figure

1 Find the first significant figure

The first significant figure is the first digit that is not 0.

In 39.2, it is 3.

= 39.2

significant figures: counted from

the first digit that is not 0

2 Count the figures

We count 1 figure from there: 3.

The 1st figure, 3, is in the tens place.

So we round to the nearest ten.

= 1st figure 3 → the tens place

3 Look at the next digit

Now we look at the next digit to the right.

It is 9.

5 or more: we round up.

4 or less: we round down.

9 is 5 or more, so we round up.

= 9 is 5 or more → round up

5 or more → up: digit + 1

4 or less → down: digit stays

4 See it on a number line

39.2 is closer to 40.

5 Keep the size

The places after the 1st figure become 0.

The zeros keep the size: 40 is close to 39.2.

= 39.2 ≈ 40

Careful!

4 is much smaller than 39.2.

The zeros keep the number the right size.

Careful: not 39.2 ≈ 4 ✗

So 39.2 to 1 significant figure is 40.

6 Check

Let's check.

40 has 1 significant figure: 4.

40: figures 4 → 1 s.f.

And it is the same size as 39.2: 2 digits before the point.

So the answer is right!

39.2 and 40: both 2 digits before the point

Let's look back.

First: find the first significant figure.

Then: count the figures.

Then: look at the next digit.

Then: see it on a number line.

Then: keep the size.

Last: check.

Answer