The Fathers' Day card

Achievement Objectives
NA3-1: Use a range of additive and simple multiplicative strategies with whole numbers, fractions, decimals, and percentages.
Student Activity


Niko and Kaia buy their father a card for Fathers’ Day.

The card costs $5.90. Niko puts in 40c more than Kaia.

How much do they each contribute to the card?

 

Specific Learning Outcomes
Subtract using decimals
Find ½ of a decimal number
Devise and use problem solving strategies (act it out, draw a picture, guess and improve, make a table)
Description of Mathematics

This problem involves a two-digit subtraction and division by 2 and can be solved using a number of strategies. The greater challenge is in the extensions to the problem which require the students to think about the multiples of numbers.

Activity

The Problem

Niko and Kaia buy their father a card for Fathers’ Day. The card costs $5.90. Niko puts in 40c more than Kaia. How much do they each contribute to the card?

Teaching Sequence

  1. Pose the problem and ask students to restate it in their own words.
  2. Circulate as students work on the problem, asking them to explain the strategy that they are using.
  3. Share solutions.

Extension to the problem

Have students:

  • write a similar problem with higher values.
  • write a problem in which three people share the cost.
  • write a similar problem in which a fraction of the cost is given instead of a $ value.

Other contexts for the problem

Purchasing a gift, sharing the cost of a meal

Solution

If Niko had not put in the extra 40c, they would have only paid $5.50. 
Divide by 2 to find Kaia's share: $5.50 ÷ 2 = $2.75
Niko contributes $2.75 + $0.40 = $3.15.

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