MYP maths criterion B and D tasks

Most MYP maths marks come from tasks your teacher sets and marks. Here is one of each kind to try, with a model answer for when you've had a go.

Criterion B is investigating patterns: try cases, spot the pattern, write a rule and test it. Criterion D is using maths on a real problem and judging whether your answer makes sense. Your teacher marks each one from 0 to 8.

Criterion B · Investigating patterns · MYP 3

Handshakes

At a meeting, everyone shakes hands once with everyone else.

  1. Work out enough cases to see a pattern, and organise them in a table (for example n = 2, 3, 4, 5, 6).
  2. Describe the pattern and write a general rule using n.
  3. Test your rule on a new case that is not in your table.
  4. Explain why the rule works.
Show me a model answer

What earns a 7–8: Explains why the rule works (each person shakes n - 1 hands and each handshake is counted twice) and uses it for a large group.

  1. I worked out the first cases carefully and recorded them: n = 2: 1; n = 3: 3; n = 4: 6; n = 5: 10; n = 6: 15; n = 7: 21.
  2. Pattern: see the differences between the values in my table.
  3. General rule: n(n−1)2.
  4. Test: for n = 9 I counted 36 the long way, and the rule gives 36, so they agree.
  5. Why it works: Each of the n people shakes n - 1 hands, giving n(n - 1), but every handshake involves two people so it has been counted twice.

Criterion D · Applying maths in real-life contexts · MYP 3

Which mobile plan?

Plan A costs €8 a month plus €2 per GB of data. Plan B costs €20 a month with unlimited data. Your phone records show this monthly data use (GB): 4.5, 6.0, 5.2, 7.8, 5.5, 6.4.

Illustrative prices and usage made up for this task
Plan A€8 + €2 per GB
Plan B€20, unlimited
Use (GB)4.5, 6.0, 5.2, 7.8, 5.5, 6.4
  1. Identify the relevant information: what do you know, what do you need to find, and what can you ignore?
  2. Choose a mathematical model or strategy and say why it suits the situation.
  3. State the assumptions you are making.
  4. Solve the problem, showing your working.
  5. Check your answer: units, accuracy and rounding.
  6. Is your answer reasonable in real life? Justify it.
  7. Suggest how the model could be improved, or what extra information would help.
Show me a model answer

What earns a 7–8: Also discusses variation between months and the assumptions, and justifies a recommendation.

  1. Relevant: both prices and the six months of data use.
  2. Model: cost of A = 8 + 2g for g GB. A and B cost the same when 8 + 2g = 20, so g = 6 GB.
  3. Mean use is 5.90 GB, just below 6 GB. Over the six months A would have cost €118.80 and B €120.
  4. Assumption: future use is like the last six months. In the month with 7.8 GB, B was cheaper.
  5. Judgement: A is slightly cheaper on average, but B protects against heavy months. Improvement: use a full year of data and check for extra charges.

Teachers: our task bank has 15 criterion B and 15 criterion D tasks for MYP 1 to 5, each with student sheets and level descriptors in our own words. Open the task bank with a free teacher account.

How the 0–8 levels become a grade: how MYP maths grades work.

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