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Addition & Subtraction
Objectives
To apply learnt strategies for mental calculations involving addition and subtraction and to establish a favoured method.
Resources
Abacus 4 Textbook 3 | Squared paper
Today's Lesson
Main Activity
For the mental warm ups for this week, ask your student to recite two times tables each day. Call out random questions on these two tables every day, including corresponding division facts.
Turn to page 48 in Abacus 4 Textbook 3.
Watch 'Mental Addition'.
Talk about the different mental strategies that could be used for working out the calculations.
Remind your student, for example, of the method where number bonds to multiples of 10 are found first.
Another method could be to add the tens first, then to add the ones and adjust the answer if it breaks a tens barrier.
A further method could be to round up or down to the nearest 10, add the multiples of 10 and then adjust the answer accordingly at the end.
(Please note, you might find one strategy the easiest for you, but your student may find another works better. It is very much a personal matter. Do not try to persuade your student to work with your method, if their choice is different to yours.)
Once your student has identified a method or methods that works best for them, encourage them to copy and complete the calculations mentally.
Look at the problems and talk together about how your student could go about working these calculations out mentally, as well.
Ask your student to complete the page.