Here are our classroom rules.

Remember that F.A.I.L means First Attempt In Learning.

From last time we know:

- What a cuboid is compared to, for instance, a cube.
- How to calculate the volume of a cuboid (and a cube).
- Know how to round off to a given number of decimal places.

*Can I calculate a volume of a two-dimensional shape, like for example a rectangle?*

*Is it enough information if I know the length of one side in a cube to calculate the volume?*

### The general rounding rules are:

- If a digit after the one being rounded off is less than 5, we round down.
- If a digit after the one being rounded off is 5 or more, we round up.

Examples:

- Round 254 to the nearest 10th.

*Since the 5 is the 10th, we look at the number after which is a 4. Since it is a 4 we round the number down, i.e 254 to the nearest 10th is 250.*

2. Round 7.2614 to 1 decimal place.

*Since one decimal place is where we have a 2, we look at the number after the 2 which is a 6. Since it is a 6 we round the number up, i.e 7.2614 rounded to 1 decimal place is 7.3.*

### Today’s lesson

**Learning goals:**

- Know how to round off to a certain number of significant figures.
- Understand the difference between the concepts
*decimal places* and *significant figures.*
- Know that you always should round to three significant figures if nothing else is stated (in the IB).

**Starting activity:**

Guess the height of the person sitting next to you.

Give your answer correct to 3 significant figures in centimeter.

Give your answer correct to 4 significant figures in centimeter.

Which measurement ”tries” to be more exact than the other one?

Convert the height into decimeters, meters and kilometers. Has the values accuracy changed?

**Theory:**

If you want to be prepared, watch the video from Khan academy about significant figures.

Back to the examination question.

Work in book, p. 48

2E.1, 1-2 every other

2E2, 1

2E3, 1-4

**Exit tag.**