- Home
- Canvas Guide
Partial Progress - Circles (browser only)
Halving
Objectives
To understand that halving means ‘divide by 2’.
To work out efficient strategies for quick, easy halving.
To make a connection with the strategy for doubling and to be able to apply the same principles to halving.
Resources
Abacus 4 Textbook 1 | Squared paper
Today's Lesson
Main Activity
Think up a few train timetable questions where the number of minutes in between each time are not multiples of 5. For example, a train leaves one station at 05:32. It arrives at the next station at 06:17. How many minutes does the journey take? You could also say, for example, the train left the first station at 05:27. It arrives at the next station 26 minutes later. What time does it arrive? Jotting some working on an empty number line might support your student in visualising these time differences.
Turn to page 51 in Abacus 4 Textbook 1.
Look at the examples with your student. Tell them that we are now halving – dividing by 2. We can use the same method of partitioning for halving as we did for doubling. Point out that halving a number where all the digits are even is extremely easy. You simply consider one digit at a time and halve it. There is no need to separate the number out by partitioning, as in the example. However, if there is an odd number within the number, it is best to partition, as in the example.
Watch this video to recap on partitioning when halving 3-digit numbers.
Once your student is comfortable with the concept, ask them to copy and complete the calculations. Point out that halving numbers with even digits only does not need to be written out an extended way. For example:
Half of 84 = 42.