Prior knowledge.

• Explain place value with decimals
• know combinations of tenths that add to one
• Use the idea of compatible numbers to add whole numbers

Background

This activity uses the strategy of compatible numbers to add decimal numbers.  Students at this stage should be familiar with using the strategy with whole numbers.

Comments on the Exercises

Exercise 1
Asks students to identify tenths that add to one.

Exercise 2
Asks students to use <, > in sentences to show they can identify tenths that add to one, are less than or more than one.

Exercises 3 – 5
Asks students to solve problems requiring addition of decimal fractions (tenths) using compatible numbers strategy.
Exercise 3: All numbers are less than one and students make numbers up to one.
Exercise 4: Compatible numbers include one number less than one and one number greater than one.
Exercise 5: Compatible numbers could both be greater than one.

Exercise 6
Asks students to use compatible numbers in subtraction (decimal fractions).