Prior Knowledge

• Range of strategies to solve addition and subtraction problems with whole numbers.
• Understanding of place value structure including decimals

Background

In this activity students use additive strategies to solve addition and subtraction with decimal numbers.

Comments on the Exercises

Make One Tenth
Asks students to add a list of tenths by first adding up the pairs that add to 1.

Don't Subtract - Add!
Asks students to solve subtraction problems involving tenths by reversing it to an addition problem.

Near Doubles
Asks students to solve addition problems involving tenths by using the doubling strategy.  For example, 7.8 + 7.7 as 16 - 0.5 = 15.5.

2.3 + ? = 7.1
Asks students to solve problems involving tenths by jumping a whole number on a number line then jumping back in tenths.

? + 2.9 = 8.1
Asks students to solve problems involving tenths by rearranging the equation and choosing an appropriate mental strategy.

3.7 + ? = 8.9
Asks students to solve problems involving tenths by mentally jumping up a number line.

7.3 - 1.9 = ?
Asks students to solve problems involving tenths by first subtracting a whole then adding tneths to get the answer