Number: Decimals Lesson 11 Ready-to-go Lesson Slides Year 5 Sum1
Number: Decimals
Lesson 11
Ready-to-go Lesson Slides
Year 5
Sum1
Year 5 Number: Decimals Lesson 11
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23/04/2020
Year 5 Number: Decimals Lesson 11
Specialist 1-to-1 maths interventions and curriculum resources
To multiply decimals by 10, 100 and 1000
23/04/2020
Starter:
Which sequence is different?
(a) 1.75 2 2.25 2.5 2.75
(b) 6.2 5.4 4.6 3.8
(c) 0.6 1.2 1.8 2.4
(d) 2.4 2.55 2.7 2.85
(e) 9.8 8.35 6.9 5.45
(f) 13.8 11.1 8.4 5.7
Success Criteria:
❑ I can use a place
value grid to
multiply by 10, 100
and 1000
❑ I know that the
digits in a number
move when
multiplying by 10,
100 and 1000, not
the columns or
decimal point
Year 5 Number: Decimals Lesson 11
Specialist 1-to-1 maths interventions and curriculum resources
To multiply decimals by 10, 100 and 1000
23/04/2020
Starter:
Which sequence is different?
(a) 1.75 2 2.25 2.5 2.75
(b) 6.2 5.4 4.6 3.8
(c) 0.6 1.2 1.8 2.4
(d) 2.4 2.55 2.7 2.85
(e) 9.8 8.35 6.9 5.45
(f) 13.8 11.1 8.4 5.7
The sequences involve different rules, but
– if they were extended – the next number
in each sequence is the number 3. Apart
from sequence (e), where the next number
in the sequence is the number 4!
Success Criteria:
❑ I can use a place
value grid to
multiply by 10, 100
and 1000
❑ I know that the
digits in a number
move when
multiplying by 10,
100 and 1000, not
the columns or
decimal point
Year 5 Number: Decimals Lesson 11
Specialist 1-to-1 maths interventions and curriculum resources
To multiply decimals by 10, 100 and 1000
23/04/2020
Talking time:
How could you use a place-value grid to multiply 5.42 by 10?
Year 5 Number: Decimals Lesson 11
Specialist 1-to-1 maths interventions and curriculum resources
To multiply decimals by 10, 100 and 1000
23/04/2020
Talking time:
How could you use a place-value grid to multiply 5.42 by 10?
5.42 x 10 = 54.2What do you notice about how the digits of the
number behave when they are multiplied by 10?
Year 5 Number: Decimals Lesson 11
Specialist 1-to-1 maths interventions and curriculum resources
To multiply decimals by 10, 100 and 1000
23/04/2020
Talking time:
What if you multiply 5.42 by 100?
Year 5 Number: Decimals Lesson 11
Specialist 1-to-1 maths interventions and curriculum resources
To multiply decimals by 10, 100 and 1000
23/04/2020
What if you multiply 5.42 by 100?
5.42 x 100 = 542
Talking time:
What do you notice about how the digits of the
number behave when they are multiplied by 100?
Year 5 Number: Decimals Lesson 11
Specialist 1-to-1 maths interventions and curriculum resources
To multiply decimals by 10, 100 and 1000
23/04/2020
Discuss how to complete these sentences.
5.42 x 10 = 54.2
When a number is multiplied by 10, its digits shift __ place to the ____.
5.42 x 100 = 542
When a number is multiplied by 100, its digits shift __ places to the _____.
5.42 x 1000 = _____
When a number is multiplied by 1000, its digits shift __ places to the _____.
Talking time:
Year 5 Number: Decimals Lesson 11
Specialist 1-to-1 maths interventions and curriculum resources
To multiply decimals by 10, 100 and 1000
23/04/2020
Discuss how to complete these sentences.
5.42 x 10 = 54.2
When a number is multiplied by 10, its digits shift 1 place to the left .
5.42 x 100 = 542
When a number is multiplied by 100, its digits shift 2 places to the left .
5.42 x 1000 = 5,420
When a number is multiplied by 1000, its digits shift 3 places to the left.
Talking time:
What is the same and what is different about your answers?
Year 5 Number: Decimals Lesson 11
Specialist 1-to-1 maths interventions and curriculum resources
To multiply decimals by 10, 100 and 1000
23/04/2020
Use a place-value chart and counters to model these multiplications and work out the
answers.
a) 4.5 x 10 = ___
4.5 x 100 = ____
4.5 x 1000 = ____
b) 9.38 x 10 = ____
9.38 x 100 = ____
9.38 x 1000 = ____
c) 0.892 x 10 = _____
0.892 x 100 = _____
0.892 x 1000 = _____
Activity 1:
How do the counters behave when they are multiplied by 10, 100 or 1000?
Year 5 Number: Decimals Lesson 11
Specialist 1-to-1 maths interventions and curriculum resources
To multiply decimals by 10, 100 and 1000
23/04/2020
Use a place-value chart and counters to model these multiplications and work out the
answers.
a) 4.5 x 10 = 45
4.5 x 100 = 450
4.5 x 1000 = 4,500
b) 9.38 x 10 = 93.8
9.38 x 100 = 938
9.38 x 1000 = 9,380
c) 0.892 x 10 = 8.92
0.892 x 100 = 89.2
0.892 x 1000 = 892
Activity 1:
What do you notice?
Year 5 Number: Decimals Lesson 11
Specialist 1-to-1 maths interventions and curriculum resources
To multiply decimals by 10, 100 and 1000
23/04/2020
How would you complete this table?
Talking time:
x 10 x 100 x 1000
58.107
Year 5 Number: Decimals Lesson 11
Specialist 1-to-1 maths interventions and curriculum resources
To multiply decimals by 10, 100 and 1000
23/04/2020
How would you complete this table?
Talking time:
x 10 x 100 x 1000
58.107 581.07 5,810.7 58,107
Year 5 Number: Decimals Lesson 11
Specialist 1-to-1 maths interventions and curriculum resources
To multiply decimals by 10, 100 and 1000
23/04/2020
Complete the table.
Activity 2:
x 10 x 100 x 1000
14.6
0.837
3.128
7.89
1,425
64.5
Year 5 Number: Decimals Lesson 11
Specialist 1-to-1 maths interventions and curriculum resources
To multiply decimals by 10, 100 and 1000
23/04/2020
Complete the table.
Activity 2:
x 10 x 100 x 1000
14.6 146 1,460 14,600
0.837 8.37 83.7 837
3.128 31.28 312.8 3,128
0.789 7.89 78.9 789
14.25 142.5 1,425 14,250
6.45 64.5 645 6,450
Year 5 Number: Decimals Lesson 11
Specialist 1-to-1 maths interventions and curriculum resources
To multiply decimals by 10, 100 and 1000
23/04/2020
Chloe makes this number out of cards.
She then multiplies it by 100 and uses the cards to make the answer.
Chloe says, “I need some different digit cards other than 5, 4 8 and 6 to use in the
answer.”
Do you agree? Explain.
Activity 3:
5 4 . 8 6
Year 5 Number: Decimals Lesson 11
Specialist 1-to-1 maths interventions and curriculum resources
To multiply decimals by 10, 100 and 1000
23/04/2020
Chloe makes this number out of cards.
She then multiplies it by 100 and uses the cards to make the answer.
Chloe says, “I need some different digit cards other than 5, 4 8 and 6 to use in the
answer.”
Do you agree? Explain.
I disagree. When a number is multiplied by 10, 100 or 1000, its digits do not
change, they just shift to the left a number of places. The only different digits
they ever need is possibly some zeros. Chloe’s answer will contain the digits
5, 4, 8 and 6 (it is 5,486) and so she will not need any other digit cards.
Activity 3:
5 4 . 8 6
Year 5 Number: Decimals Lesson 11
Specialist 1-to-1 maths interventions and curriculum resources
To multiply decimals by 10, 100 and 1000
23/04/2020
Fatima says,
Will Fatima’s idea work? Explain your answer.
Can you think of another way that will give the same answer?
Activity 4:
Instead of multiplying by 1000,
I am going to multiply by 10,
then by 10 again and then by
10 again.
Year 5 Number: Decimals Lesson 11
Specialist 1-to-1 maths interventions and curriculum resources
To multiply decimals by 10, 100 and 1000
23/04/2020
Fatima says,
Will Fatima’s idea work? Explain your answer.
Can you think of another way that will give the same answer?
Yes – Fatima’s idea will work. 10 x 10 x 10 is 1000, so multiplying any number
by 10 three times is the same as multiplying it by 1000.
Another way of getting the same answer might be to multiply by 100, then
multiply by 10; inversely, she could multiply by 10, then by 100.
Activity 4:
Instead of multiplying by 1000,
I am going to multiply by 10,
then by 10 again and then by
10 again.
Year 5 Number: Decimals Lesson 11
Specialist 1-to-1 maths interventions and curriculum resources
To multiply decimals by 10, 100 and 1000
23/04/2020
Evaluation:
True or False?
a) When a number is multiplied by 1000, its digits shift
to the right three places.
b) If the number 52.416 is multiplied by 100, the digit 6
in the answer will be worth 6 tenths.
c) 0.025 x 1000 = 25
d) A number containing only even digits is multiplied by 10, 100 and 1000.
The three answers could contain an odd digit.
e) 6.201 x 100 = 620.1
Success Criteria:
❑ I can use a place
value grid to
multiply by 10, 100
and 1000
❑ I know that the
digits in a number
move when
multiplying by 10,
100 and 1000, not
the columns or
decimal point
Year 5 Number: Decimals Lesson 11
Specialist 1-to-1 maths interventions and curriculum resources
To multiply decimals by 10, 100 and 1000
23/04/2020
Evaluation:
True or False?
a) When a number is multiplied by 1000, its digits shift
to the right three places.
FALSE (they shift to the left!)
b) If the number 52.416 is multiplied by 100, the digit 6
in the answer will be worth 6 tenths. TRUE
c) 0.025 x 1000 = 25 TRUE
d) A number containing only even digits is multiplied by 10, 100 and 1000.
The three answers could contain an odd digit. FALSE – they remain even!
e) 6.201 x 100 = 620.1 TRUE
Success Criteria:
❑ I can use a place
value grid to
multiply by 10, 100
and 1000
❑ I know that the
digits in a number
move when
multiplying by 10,
100 and 1000, not
the columns or
decimal point