Transcript Use halving two or three times to divide by 4 or 8

Objectives:
• Use halving two or three times to divide by 4
or 8
• Divide by 5 by dividing by 10 and doubling
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Stepping Up Term 2
Week 5 Day 3
What is an efficient mental strategy for
calculating 124 ÷ 4?
halve and halve again
20
100
4
Half of 120 is 60
Half again = 30
Half of 4 is 2
Half again = 1
124 ÷ 4 = 30 + 1 = 31
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Stepping Up Term 2
Week 5 Day 3
Which of these calculations would be tricky to
work out that way? 248 ÷ 4 237 ÷ 4 752 ÷ 4
We can extend this efficient mental
strategy by halving three times
for dividing by 8, e.g. 200 ÷ 8
© Hamilton Trust
Stepping Up Term 2
Week 5 Day 3
200 ÷ 8 …
200
halve
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100
25
50
halve again
Stepping Up Term 2
halve again
Week 5 Day 3
With a partner, choose three of
these divisions to solve by halving…
92 ÷ 4
464 ÷ 8
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352 ÷ 8
373 ÷ 4
Stepping Up Term 2
164 ÷ 4
720 ÷ 8
Week 5 Day 3
Another division trick… for dividing by 5
70 ÷ 5
70 ÷ 10 = 7 but dividing by 10 is twice as much dividing as
dividing by 5!
So make up for it by doubling the answer…
7 x 2 = 14
Check:
0
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70 ÷ 5 = 14
10 x 5
4x5
50
Stepping Up Term 2
70
Week 5 Day 3
These get trickier… How far can you get?
Divide by 5
÷ 10
×2
70
260
320
245
125
Check your answers using multiplication.
© Hamilton Trust
Stepping Up Term 2
Week 5 Day 3