Asking Questions and Making Predictions Disposable Nappies
Andy has an 18-month-old baby brother, Jack. Andy notices that Jack uses three to six nappies a day, depending on the brand his mother buys. Andy’s mother buys three types of disposable nappies, depending on which is available at the supermarket: brand X, brand Y and brand Z. Andy notices that Jack uses three brand X nappies, five brand Y nappies and six brand Z nappies in a day.
The following table shows the price of the nappies. Brand of nappy Cost
X Y Z
20 nappies for €10.00 20 nappies for €9.00 40 nappies for €10.00
1 Calculate the price of one nappy from each brand to complete the table.
Step 1: Prior knowledge and experience Before starting any investigation, it is useful to make a note of all the relevant information you already know. This will help you to make decisions and predictions about what you will test.
2 Make notes about anything you know about disposable nappies. Why are they needed? What materials are they made from? What brands could Andy’s mother have bought at the supermarket? Are nappy age or size related? Do you know anything else about nappies?
Step 2: Asking questions
Andy’s mother has asked him to investigate which nappy brand is giving her the best value for money.
3 What properties should Andy test in order to determine which nappy brand is the best value for money?
4 What predictions could Andy make based on his observations?
5 How conclusive would these observations be? Is there anything else that Andy would need to consider?
