7. Complete the following, using the examples in the box (previous page) to help you. a) 4 × 50 = (4 × 10) × 5 = c) 7 × 20 = (7 × ) × e) 8 × 30 = ( × g) 6 × 90 = ( ×


=


) × ) ×


Example 1:


40 × 20 = (40 × 10) × 2 40 × 20 = 400 × 2 = 800


= = =


b) 2 × 80 = (2 × 10) × d) 3 × 60 = ( × f) 5 × 70 = ( × h) 9 × 40 = ( ×


Example 2:


50 × 70 = (50 × 10) × 7 50 × 70 = 500 × 7 = 3500


8. Complete the following, using the examples in the box above to help you. a) 30 × 50 = (30 × 10) × c) 40 × 30 = ( × e) 90 × 20 = ( × g) 20 × 30 = ( ×


) × ) × ) ×


Long Multiplication


The 4th class school tour cost €27 per person. If there were 23 children in Mr Cleary’s 4th class, how much did the class tour cost altogether?


27 × 23 = (27 × 3) + (27 × 20) Example A:


× 2 3 8 1


2


× 2 0 5 4 0


1


T U 2 7


Step 2: Multiply 27 by 20. Write down 0 and multiply 27 × 2 as normal


H T U 8 1


5 4 0 6 2 1


1 Step 3: Add 81 + 540


T U 2 7


Step 1: Multiply 27 by 3 as normal


Example B: H T U


2 7 2 3 8 1


2


H T U 1


5 4 0 1


H T U 2 7 2 3


+ 5 4 0 6 2 1


1 8 1


2 7 2 3 8 1


Step 2: Multiply 27 by 20. Write the answer. Write down 0 first and multiply 27 × 2


Step 3: Add 81 + 540


Step 1: Multiply 27 by 3 as normal


= = =


b) 60 × 50 = ( × 10) × d) 70 × 40 = ( × f) 80 × 50 = ( × h) 50 × 40 = ( ×


) × ) × ) ×


=


= = =


=


) × ) × ) ×


= = =


Multiplication 2


85


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