These exercises and activities are for students to use independently of the teacher to practice number properties.
Using jumping the number line strategy to add decimal fractions (tenths and hundredths).
Addition and subtraction, AM (Stage 7)
Prior knowledge.
- Use the strategy jumping the number line with whole numbers (Book 5 page 33)
- Identify the place value of the tenths hundreds and thousandths columns.
- Make combinations of tenths and hundredths that add to one
Background
In this activity students use additive strategies to solve addition and subtraction problems involving decimals. Students need to have a good understanding of place value to make sense of the strategies with decimals.
Comments on the Exercises
Exercise 1
Asks students to solve problems by jumping a whole number and then a decimal. For example, 6 + ? = 8.55, 6 + 2 = 8, 8 + 0.55 = 8.55 so the answer is 2.55.
Exercise 2
Asks students to solve problems by jumping to the nearest whole number, then the next whole number and then make a decimal jump. For example, 4.97 + ? = 8.12, jump 0.03 to 5, then 3 from 5 to 8, then 0.12 to 8.12
Exercises 3 and 4
Asks students to reduce the number of jumps they used in Exercise 2. For example, 3.98 + ? = 9.3, jump 0.02 to 4 then 5.3 to 9.3.
Exercise 5
Asks students to choose their own strategy to solve problems like 11.82 + ? = 38.3.
Exercises 6 and 7
Asks students to solve problems like in Exercise 5 but the numbers are larger, for example 19.88 + ? = 224.52
Written recording
Written recording of mental strategies (that is, how you thought through the problem) is important for developing sound assessment skills as it allows others to follow your reasoning and allows you to have a visual check for accidental errors. It is also something that develops over time, and needs to be discussed regularly with students. Exercises 5, 6 and 7 stress that students should solve the problems mentally, but record enough to show what they have done. Discussing or eliciting different ways of doing this is therefore an important activity, which you may choose to run either before or after setting students to work on this exercise