This problem solving activity has a number focus.
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?
- 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).
This problem involves a two-digit subtraction and division by 2. It 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.
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
- Pose the problem and ask students to restate it in their own words.
- Circulate as students work on the problem, asking them to explain the strategy that they are using.
- Share solutions.
Extension
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.
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.