Purpose

In this unit we investigate the amount of water contained in a carrot and we plot the "weight" of the carrot using a line-graph as the water in the carrot evaporates. The students also pose their own carrot questions for investigation.

Specific Learning Outcomes
  • plan an investigation
  • choose an appropriate data display (bar chart, stem-and-leaf, strip graph, line graph)
  • make statements about the findings of the investigation
Description of Mathematics

You should be expecting students at Level Three, to take an increasing responsibility for the planning and conducting of statistical investigations. Here they can talk about situations they have experienced, pose questions for an investigation and produce a plan for a statistical experiment. Students may be capable now of incorporating a computer into their work.

At Level 3 the students are introduced to stem-and-leaf graphs, dot plots and strip graphs. Depending on the nature of the questions they are posing, they will find out that they need to collect and organise the data in different ways. When considering the data they now start to see and talk about distinctive features of their displays such as outliers and modes.

Number Framework Stage 6, Advanced Additive.

Required Resource Materials

Scales (finely calibrated)

Graters

1 kg of carrots

Packets of carrot seeds

Key Vocabulary

 stem-and-leaf graphs, dot plots, strip graphs, line graph, percentage, investigation, evaporation, dehydration,

Activity

Getting Started

  1. We begin the unit by bringing along a kilogram of carrots and posing the question:
    How much of a carrot is water?
  2. Get the students to brainstorm how much they think. Encourage all answers. Conclude by asking the students to estimate as a percentage of its weight.
  3. Ask: How can we find out?
    Again get the students to share their ideas.
  4. Select one of the ideas to use for the investigation. One way is to weigh the carrots, without the green tops, then grate them and leave the carrots to dry in the sun (or you could use a dehydrator).
  5. Over the week weigh the carrots (twice daily) keeping a record of the weights on a bar chart. Alternatively a line graph (introduced at Level 4 of the curriculum) is an appropriate data display for this data.

graph

 

  1. After about a week the carrot should be dried out completely.

Exploring

Over the next three days the students in small groups plan and conduct their own carrot investigation.

  1. Brainstorm some other things that the students could find out about carrots. Some ideas include :
    - How many seeds are there in a packet of carrots?
    - Is it cheaper to grow or buy carrots?
    - Where is the cheapest place to buy carrots in New Zealand this week? (fax or ring supermarkets around New Zealand.)
    - Is there is a relationship between the length of green top on a carrot and the length of the carrot? (this one is only possible in spring)
    - Do carrots get a fair deal in the Frozen Mixed Vegetables Packets?
    - Which carrot cake recipe tastes the best? (this requires some supportive home help)
  2. Allow the students to select and plan their investigation, collect their data and interpret it.
  3. It is important that you circulate around the groups asking questions to that help the students plan and them make sense of their investigation. In the early stages it is important that they have a clear strategy for collecting data that will help answer their question.
  4. Ask the students to prepare an oral presentation supported by a graph for sharing with the class on the final day of the unit.

Reflecting

On the final day we look at look at and interpret the findings of our line graph. We also share our small group investigations with the class.

  1. As a class discuss the finished weight and work out what percentage of the carrot must have been water because it has evaporated.
  2. Ask the students, in pairs or small groups, to present this fact in an interesting way. (One idea is to draw a carrot with the percentage of water coloured blue and the remainder orange.)
  3. Display around the class for the pot-luck tea.
  4. Oral presentations by the groups on their investigations. These presentations could be repeated to parents at a Carrot Pot Luck Tea.

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