BeMED 13. BIDMAS with Marine Litter

BIDMAS with Marine Litter
Christian Saliba
Age Guide
Year 6
Subject Area
Preparation Time Nil
Estimated Duration 45 – 50 minutes
Site Classroom
Educational objectives Through problem solving and the practice of addition, subtraction, multiplication and division, the students will learn about the harm so many items are causing on our environment when we throw them away haphazardly, regardless of the length of time they take to decompose.
Learning Outcomes – I can select and use an appropriate operation and strategy when solving a problem.

– I can rehearse adding/ subtracting ThHTU ± ThHTU using informal and standard written methods.

– I can check the result of a calculation and/or real life problem by using an equivalent calculation or an inverse operation.

– I can use the relationship between addition and subtraction.

– I can consolidate the understanding and the usage of the four operations.

– I can use written methods for:  HTU × TU/U.

Link to SDGs SDG 3: Good health and well-being

SDG 11: Sustainable cities and communities

SDG 13: Climate action

SDG 14: Life below water

Educational resources required Small whiteboard per group

Appendix 13.1 – Fact sheet

Appendix 13.2 – Flashcards with the questions (need to be printed and cut separately)

Appendix 13.3 – Questions and answers for teachers


Internet connection

Remote preparation The teacher will discuss with the students the damage done to marine life. The students will also be provided with a fact sheet (Appendix 13.1) which will give them information on how long it takes for different types of litter to decompose.
Planning Considerations It would be interesting to take the students near the seashore, and see floating litter, or litter on the shore, to become more aware how serious and actual this problem is. An alternative to the outing, one can show the following videos showing the local marine litter.



Method Introduction

This activity is targeted for students in year 6 who already have the knowledge and ability to work out sums in addition, subtraction, multiplication and division.  Marine litter will be incorporated with story sums to increase awareness regarding marine litter.

o     Development

The class is divided into 4 groups – A, B, C, D – at the beginning of the lesson. A small white board will be given to each group. A video ( related to marine litter is shown to the students, after having told them to pay attention since afterwards they will need to participate in a conversation related to what they see in the video. When the video ends, the educator will ask the students to describe what they have seen and mention some facts.

After the introductory video the competitiveness and fun will kick in. The student will be shown another video related to marine litter but this time the students will be asked to write items that contaminate marine life as shown on the video

( This video is “Sources and impacts of marine litter” by Jane Lee/ Marlisco. After the video, 3 minutes will be given to the students to write down the items they have seen in the video. When time is up students will read out the answers and be given credit.

While the students are writing the answers a fact sheet (Appendix 13.1) will be distributed to each group to be used in the main activity. Rules will be explained to the students before the start of the activity.

Starting with the first group, the group leader selects a flashcard from the desk and the teacher will read the story sum out loud. As soon as the teacher finishes reading a 2-minute timer will start. All groups have to work out the sum collaboratively. A sample question is as follows:

If plastic bottle A was thrown at sea in 2000, bottle B in 2021 and bottle C in 2030, which bottle or bottles will still be found in the sea if aliens come to  visit Earth in the year 2462?

A: 2000+450=2450

B: 2021+450=2471

C: 2030+450=2480

Answer: Bottle B and C

(All questions can be found in Appendix 13.2.  Questions with answers can be found in Appendix 13.3)

The students will be asked to sum up years and months or multiply, etc to give an answer. In others the students have to look up amounts from the fact sheet distributed earlier.


·       Different questions require different computations and have different weighting as regards point.

·       Some of the questions require students to add up the total length of time of decomposition of different items when in reality the answer is not significant.    If a student/group points out that the total does not make sense and explains correctly why, the group is given bonus points at the discretion of the teacher.

·       Some of the questions are trick questions (stared*) which do not require any calculations.  Refer to Appendix 13.3.


After settling back down in their places, the students will be asked random questions related to marine litter for instance ‘How long does it take for a cigarette butt to decompose?’. This will help the students to be more aware of the impact such “insignificant” items have on marine life.

Follow-up activities After the activity the teacher can ask the students to rank the items according to the time they take to decompose.

As a follow-up activity, maybe a week or so later, it would be interesting to ask the students at random, without any previous notice, how much time do different items take to decompose, in order to have them recall the info given in the fact sheet (Appendix 13.1) given out during the main activity.

Background information for educators Refer to Appendix 13.1 and video links used in method.

Sheet facts data from:’s_gone.jpg

Adaptations For students with learning difficulties:

The learning support educators can help them out with the working of difficult problems (or maybe the use of a calculator will be allowed).

Extensions For gifted students:

Asking students to write a problem themselves and present it to the class.