Sea Level

Sea Level

Sea Level printable sheet

What can you see in this picture? You can click on it to make it bigger if you would like a closer look.

 

 

There are black markings all the way up the lighthouse right to the very top, and on the rock that the lighthouse is built on, going down to the sea bed. These markings are 1 metre apart.

We will call sea level '0' and then we could think of the lines as representing positive numbers going upwards and negative numbers going down to the sea bed.

In this task, we are going to look at where the mouths of each of the different animals are. This will allow us to see how deep they are compared to each other, or what distance apart they are.

For example, the seahorse's mouth is 1 metre deeper than the mouth of the blue and yellow fish.

Have a think about these questions, or you might like to make up some of your own:

1. What number should be where the head of the seagull is?
2. What number should be where the mouth of the crab is?
3. How far up is it from the head of the shrimp to the mouth of the shark?
4. How far from the surface is the eel's mouth?
5. How high above the sea level is the seagull's beak?
6. How much higher is the seagull's beak than the seahorse's mouth?

How did you arrive at your answers? Did you write anything down to help you?

Why do this problem?

This problem is a good way to increase familiarity with negative numbers on a number line. In answering the questions, children begin to calculate with negative numbers in a context that will give them confidence rather one which they perceive as difficult.

Possible approach

It would be a good idea to print out the picture so that children can put on the numbers and more easily use a ruler to see which objects are at a certain level. To make the link with calculation more explicit, you could have a go at writing number sentences for some of the questions as a class, then challenge the children to complete number sentences for the other questions. Pupils can then go on to invent questions of their own and, in particular, they could find alternative ways of asking the same question. For example:

Key questions

Tell me about the depth of these fish.

Possible extension

You could invite children to make up as many questions as they can which have, for example, the answer $3$m. This allows them to be as creative as they like, and is a good way to assess their understanding.

Possible support

Some children will benefit from having a go at the Swimming Pool problem before this one.