Ready-to-go Lesson Slides Year 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

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


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




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:


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




23/04/2020

Talking time:

How could you use a place-value grid to multiply 5.42 by 10?




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?




23/04/2020

Talking time:

What if you multiply 5.42 by 100?




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?




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:




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?




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?




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?




23/04/2020

How would you complete this table?

Talking time:

x 10 x 100 x 1000

58.107




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




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




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




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




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




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.




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.




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:


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




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:


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

Documents

Ready-to-go Lesson Slides Year 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