Worth the Work

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Purpose

This is a level 3 number activity from the Figure It Out series. It relates to Stage 6 of the Number Framework.
A PDF of the student activity is included.

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

Click on the image to enlarge it. Click again to close. Download PDF (359 KB)

Specific Learning Outcomes

solve problems involving money

Required Resource Materials
FIO, Level 3, Number, Book 3, Worth the Work, page 10
Activity

In this activity, students solve money problems involving addition and subtraction, use estimation skills, and extract information from a table.
Some students may need to discuss the numbers in the table because they may not, at first, agree with the amounts in the Pay to date column if they forget to take into account the fact that a job may be done more than once a week. For example, Rachel does the dishes 3 times a week at $2 a time, which is $6 x 10 weeks = $60.
Question 1 should be a mental addition activity. Strategies could include basic facts knowledge and finding tens and hundreds: 60 + 40, 150 + 55.
In question 2, discourage the students from using a calculator and possibly even a pencil and paper. The mental strategy for taking $199 from $445 could be to round $199 to $200, take the $200 away from $445 to make $245, and then add $1 more to make $246.
Question 3 initially looks difficult, but it can be done by taking away $30 and then adding 5 cents. The students could try doing this mentally.
For question 4, again encourage the students to look for a way they can solve the problem in their heads. Before they start, make sure everyone understands that they need to consider the cost of the skateboard and helmet and the pads as well as the amounts mentioned in question 4. One strategy is: $19.90 is close to $20; 20 + 50 = 70, and $70 – 10 cents = $69.90. The students then need to add the cost of the skateboard and helmet and the pads.
Ask the students:
“Is it quicker to find the answers by working mentally, using a pencil and paper, or using a calculator?” “What must you know if you are to ‘believe’ the calculator’s answers?”
The students will hopefully see that working mentally will often be quicker because pencil and paper methods can be slower and more tedious. For the calculator to be an effective tool, the students must be able to estimate the answer so that they know if they have pushed the correct buttons. Estimation skills require quick recall of all basic facts, number sense, knowledge of place value, and multiplying and dividing by 10, 100, and so on.
After the students have completed the page using mental strategies, they could check their own work with a calculator and share their strategies with a classmate.


Further discussion and investigation

The students could look at some current advertising material and work out some more problems based on buying items listed in the advertisements with a set amount of money.
If appropriate, have the students make a table of the money they have received from jobs done around the home and work out how much they could save in 10 weeks. If they had a special item they wanted to buy for themselves, how long would they have to work in order to afford it?

Answers to Activity

1. $445.00
2. $246.00
3. $216.05
4. a. $298.85
b. $146.15

Attachments
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Level Three