TOPIC
Long Multiplication
Strand: Number
Strand unit:
410
Develop and recall multiplication facts within 100.
411.2 Multiply a 2-digit or a 3-digit number by a 2-digit number.
412
Solve and complete practical tasks and problems involving multiplication of
whole numbers.
416
Use a calculator to check estimates.
Looking back: What the 3rd class programme covered
1.
2.
3.
4.
Multiplication as repeated subtraction.
Zero, commutative and distributive properties of multiplication.
Multiplication facts within 100.
Multiplying a 1-digit by a 2-digit number and related problems and practical tasks.
Maths skills used in this topic
1. Applying and problem-solving: Apply mathematical concepts and processes, and plan and
implement solutions to problems, in a variety of contexts.
2. Integrating and connecting: Make mathematical connections within mathematics itself,
throughout other subjects, and in applications of mathematics in practical everyday contexts.
Calculator
Vocabulary
Multiply, add the same number lots of times
Teaching points
Children must understand that when multiplying a number by say, 47, the 4 represents 40. First we
multiply by 7, then we multiply by 40. Hence the rule: ‘Write a zero and multiply by 4.’
Fans:
Multiplication facts. Show the factors for any given number to 100. Use different forms of
language, e.g. ‘What is the product of 9 x 8?’, ‘Show 8 bundles of 4.’, ‘What is 5 times 9?, ‘Double
each number’.
65
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Multiply 24 by 10, repeat with other numbers.
Target board 3:
How many 25s are in each number? The children could be given a blank grid
and work in pairs to fill in the grid.
Topic suggestions
Alternative means of teaching long multiplication – lattice method. This method dates back to the
Middle Ages! (Shown here to illustrate that there are other ways to tackle long multiplication.)
Example: 43 x 92
4
4x9
3
4
3
2
3
9
4
6
7
3x9
3
2
3
9
4
3
6
7
9
3x2
0
0
0
2
2
8
2
6
3
4x2
6
2
3
9
7
0
8
5
9
2
Answer
3,956
6
6
Activity A
Tables drill with a difference
Instead of calling out the numbers, e.g. ‘6 times 8’, choose a colour from each wheel. Children
must locate the numbers in that section and compute the product, e.g. ‘Purple by white’ (35).
Differentiation
Lower attainers:
Refer to photocopiable.
Higher attainers:
Investigate age: The question in the text (page 88(B)) where the aliens’ ages in days are worked
out assumes that their ages are computed on their actual birthdays. Ask the children to work out
their own age in days and to include the number of days since their last birthday. You can extend
this activity to age in weeks or age in hours.
Topic
Topic
1. You work in a sweet factory and your job is to work out the prices for the sweet orders that
1. Practise multiplying by 10.
(a) 10 x 23 ______
(b) 10 x 36 ______
(c) 10 x 45 ______
(d) 10 x 58 ______
(e) 10 x 67 ______
(f) 10 x 75 ______
(g) 10 x 84 ______
(h) 10 x 124 ______
(i) 10 x 235 ______
(j) 10 x 357 ______
(k) 10 x 448 ______
(l) 10 x 172 _____
2. (a)
53
(b)
72
86
(c)
(d)
41
(e)
99
x 40
x 60
x 30
x 80
x 90
3. (a) 124
(b) 215
(c) 319
(d) 408
(e) 318
x 20
x 30
x 20
x 20
x 30
come in from sweet shops. This is your price list.
Chocolate Beans
Toffee Twirls
Turkish Delight
Party Allsorts
75
(f)
x 50
50c
60c
88c
95c
Mellow Mallows
Coffee Cubes
Torpedo Tubes
Fizz Bombs
15c
99c
80c
75c
(a) Cindy sent an order for 60 chocolate beans and 75 Torpedo Tubes. ____________
(b) The Candy Corner ordered 55 Fizz Bombs and 16 Coffee Cubes. ____________
(f)
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(c) The Kokonut needed 45 Chocolate Beans, 65 Turkish Delights and 40 Mellow Mallows.
x 20
____________
(d) Susie’s Snax wanted 20 Toffee Twirls, 42 Party Allsorts and 15 Torpedo Tubes. ____________
4. (a)
53
(b)
x 18
37
94
(c)
x 16
(d)
x 13
86
(e)
x 15
79
81
(f)
x 16
(e) McKeons put in an order for 1 dozen Toffee Twirls, 2 dozen Coffee Cubes and 3 dozen
x 19
Torpedo Tubes. ____________
(f) The Gala asked for 25 Chocolate Beans, 25 Turkish Delights, 25 Mellow Mallows and 25
5. (a)
23
(b)
x 37
59
72
(c)
x 24
6. Choose the correct answer.
(a) 49
(b) 53
(d)
x 48
87
(e)
x 56
96
x 72
Fizz Bombs. ____________
86
(f)
x 38
(g) Turners ordered 20 of each item. ____________
(h) Michael’s Corner ordered 10 Torpedo Tubes and 15 of everything else. ____________
(e) 88
(f) 96
x 49
x 53
x 72
x 65
x 88
x 96
2,321
424
5,184
4,205
1,408
9,261
2,401
414
(c) 72
648
(d) 65
4,225
7,084
9,126
637
none of
these
2,809
none of
these
638
none of
these
715
none of
these
7,744
none of
these
9,612
none of
these
2. (a) A skydiver falls at a rate of 52m per second. How far will she fall in a minute? ____________
(b) How many bottles are stored in a warehouse that has 6 pallets, each with 20 crates? Each
crate holds 24 bottles. ____________
(c) How many panes of glass do I need for a glasshouse that has 18 windows. Each window has
8 panels and each panel is double glazed (has two panes of glass). ____________
(d) What change will I get from €1,000 if I buy 8 games at €76? ____________
7. Do these in your head. Example: 40 x 90 = 3,600
(f) 40 x 50 = ______ (g) 60 x 90 = ______ (h) 70 x 30 = ______
8. Amy won a case of fruit juice cartons. Each carton contained 250m¬ of juice and the case had
24 cartons. Amy wants to mix all of the juice in a very large bowl for a party. How much does
the bowl need to hold? _____________
Name: _______________________________________
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Date: ___________________
(e) What is 15 x 15 x 15? ____________
(f) If your heart beats 72 times in one minute, how many times will it beat in one hour?
____________
(g) How many photos can I carry on 12 memory cards if one card can hold 512 photos?
____________
Name: _______________________________________
Date: ___________________
© Folens Photocopiables
(b) 30 x 80 = ______ (c) 60 x 70 = ______ (d) 90 x 20 = ______
(e) 20 x 50 = ______
© Folens Photocopiables
(a) 20 x 90 = ______
Linkage
Number: Operations (addition)
Integration
SESE Science: Science data often requires that we work out the product, e.g. total consumption of
fizzy drinks if 20 children drink 15 litres each a month. How many seeds can germinate if we plant
12 packets, each with 48 seeds?
Maths at home/parental involvement
Can you find any example of long multiplication at home and around us?
Mum paid for 14 litres of milk at €1.60 per litre. The school bus carried 35 pupils twice a day
for 15 days. The hurling blitz had 18 squads of 15 players. Dad won a hamper of tea bags – 25
boxes with 80 tea bags per box. A lightbulb uses 18 watts of power every hour – how many
watts are used in 35 hours?
Notes
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