Unit 24–3
Student page 72
Indicators
Outcomes N3.3, N3.1, N3.2
The student is able to: • understand that multiplication can be used for repeated addition situations. • partition two-digit numbers to assist in adding and subtracting them mentally.
Skills • multiplying • adding • doubling
Memory Masters (N3.3)
Resources • Base 10 MAB • calculator • counters/cubes
Language • double • add • multiply
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Number (N3.3)
• Students choose and use a repertoire of mental, paper and calculator strategies, meeting needed levels of accuracy and judging the reasonableness of results.
Main Activity (N3.2, N3.3) Warm up
• Distribute counters or cubes to groups of students. Ask students to nominate numbers between 1 and 20. Students then make that amount with the counters or cubes, placing them in a row. • Ask students to place another row next to the first. Ask what they have made. (Multiplying by two, adding the same number again or doubling.)
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• Direct students to Exercise 3. Complete the activity mentally or by using counters to assist. • Discuss how they could double the numbers mentally in Exercise 4. All numbers in this section can be doubled by doubling each digit; e.g. 23—2 + 2 = 4 and 3 + 3 = 6; i.e. 46. • Exercise 5 requires mental or written regrouping for most of the numbers. Students may wish to use counters, cubes or a calculator to assist if necessary. • Ask students what they noticed about all the answers in each exercise. After discussion, students write an answer for Exercise 6. (When numbers are doubled, the answers are always even, regardless of whether the original number was odd or even.)
Challenge
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What to do
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• The focus for this unit is basic facts of multiplication with subtraction of a single-digit number.
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• Ask students what they think consecutive numbers are. • Give examples of two consecutive numbers such as 41 and 42. • Present students with the problem: ‘The answer to a problem is 107. Find the two consecutive numbers, when added together, make 107.’ • Students give a brief explanation of how they found the two numbers.
• 116 • New Wave Maths Book D – Teachers Guide
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