1. Created by Mr. Lafferty Maths Dept.
Whole Numbers
National 4
NUM 1.2
Rounding to nearest 10,100,1000
Estimating Answers
Multiplying & Dividing by 10,100,1000
Multiplying & Dividing by 20, 300 etc..
19-Apr-17
Created by Mr. Lafferty Maths Dept.

2. Created by Mr. Lafferty Maths Dept.
Starter Questions
National 4
NUM 1.2
28o
19-Apr-17
Created by Mr. Lafferty Maths Dept.

3. Created by Mr. Lafferty Maths Dept.
Whole Numbers
National 4
NUM 1.2
Rounding to nearest 10, 100 and 1000
Learning Intention
Success Criteria
1. Understand the rules for rounding to the nearest 10, 100, 1000.
1. To round numbers to the nearest 10, 100 and 1000.
2. Apply rules to problems.
19-Apr-17
Created by Mr. Lafferty Maths Dept.

4. Created by Mr. Lafferty Maths Dept.
Whole Numbers
National 4
NUM 1.2
Rounding to nearest 10, 100 and 1000
To round to the nearest 10 : look at the units digit:
- If it is a 0, 1, 2, 3, 4 leave the 10’s digit as it is.
- If it is a 5, 6, 7, 8, 9 round the 10’s digit up by 1.
To round to the nearest 100 : look at the tens digit:
- If it is a 0, 1, 2, 3, 4 leave the 100’s digit as it is.
- If it is a 5, 6, 7, 8, 9 round the 100’s digit up by 1.
19-Apr-17
Created by Mr. Lafferty Maths Dept.

5. Created by Mr. Lafferty Maths Dept.
Whole Numbers
National 4
NUM 1.2
Rounding to nearest 10, 100 and 1000
To round to the nearest 1000 : look at the hundreds digit:
- If it is a 0, 1, 2, 3, 4 leave the 1000’s digit as it is.
- If it is a 5, 6, 7, 8, 9 round the 1000’s digit up by 1.
Example : Round 3467 to the nearest 10, 100, 1000
The nearest 10 : 3467
3470
- look at the units digit :
The nearest 100 : 3467
3500
- look at the tens digit :
The nearest 1000 :3467
3000
- look at the hundreds digit:
19-Apr-17
Created by Mr. Lafferty Maths Dept.

6. Created by Mr. Lafferty Maths Dept.
Whole Numbers
National 4
NUM 1.2
Rounding to nearest 10, 100 and 1000
Example : Round to the nearest 10, 100, 1000
The nearest 10 :
- look at the units digit :
18 570
The nearest 100 :
- look at the tens digit :
18 600
The nearest 1000 :18565
- look at the hundreds digit:
19 000
19-Apr-17
Created by Mr. Lafferty Maths Dept.

7. Created by Mr. Lafferty Maths Dept.
Whole Numbers
National 4
NUM 1.2
Rounding to nearest 10, 100 and 1000
Now try Ex 1 & 2
Last 2 columns
Ch1 (page 9)
19-Apr-17
Created by Mr. Lafferty Maths Dept.

8. Created by Mr. Lafferty Maths Dept.
Starter Questions
National 4
NUM 1.2
42o
19-Apr-17
Created by Mr. Lafferty Maths Dept.

9. Created by Mr. Lafferty Maths Dept.
Whole Numbers
National 4
NUM 1.2
Using Rounding to Estimate Answers
Learning Intention
Success Criteria
1. Be able to round numbers to a whole number.
1. To explain how estimate answer by rounding a number to an easier number for mental calculation
2. Estimate the answer to a difficult calculation using easier whole numbers.
19-Apr-17
Created by Mr. Lafferty Maths Dept.

10. Whole Numbers www.mathsrevision.com 40 x 50 = 400 x 5 = 2000
National 4
NUM 1.2
Using Rounding to Estimate Answers
It is very important when solving problems that we have
a rough idea of the answer we are expecting.
Example : Mentally estimate the answer to 42 x 49
Easiest way, is to round the two numbers first
40 x 50 =
400 x 5 =
2000
19-Apr-17
Created by Mr. Lafferty Maths Dept.

11. Created by Mr. Lafferty Maths Dept.
Whole Numbers
National 4
NUM 1.2
Using Rounding to Estimate Answers
Example : Mentally estimate the answer to 104 x 19
Easiest way, is to round the two numbers first
100 x 20 =
1000 x 2 =
2000
Example : Mentally estimate the answer to 878 ÷ 27
Easiest way, is to round the two numbers first
900 ÷ 30 =
90 ÷ 3 = 30
19-Apr-17
Created by Mr. Lafferty Maths Dept.

12. Created by Mr. Lafferty Maths Dept.
Whole Numbers
National 4
NUM 1.2
Using Rounding to Estimate Answers
Now try Ex 3
Ch1 (page 10)
19-Apr-17
Created by Mr. Lafferty Maths Dept.

13. Created by Mr. Lafferty Maths Dept.
Starter Questions
National 4
NUM 1.2
34o
19-Apr-17
Created by Mr. Lafferty Maths Dept.

14. Created by Mr. Lafferty Maths Dept.
Whole Numbers
National 4
NUM 1.2
Multiply by 10, 100, 1000
Learning Intention
Success Criteria
1. To understand how to multiply and divide simple whole numbers by 10, 100, 1000.
Understand the simple rules to multiply and divide simple whole numbers.
2. Be able do simple calculations.
19-Apr-17
Created by Mr. Lafferty Maths Dept.

15. Whole Numbers www.mathsrevision.com Multiply by 10, 100, 1000
National 4
NUM 1.2
Multiply by 10, 100, 1000
For this section you need to know your tables
To multiply by 10, 100, 1000
To multiply by 10 simply add a zero to the number
To multiply by 100 simply add 2 zero’s to the number
To multiply by 1000 simply add 3 zero’s to the number
Example : Multiply 36 by 10, 100, 1000.
Guess rule for 1000
36 x 10 =
360
36 x 100 =
3600
36 x 1000 =
36000
19-Apr-17
Created by Mr. Lafferty Maths Dept.

16. Whole Numbers www.mathsrevision.com Multiply by 10, 100, 1000
National 4
NUM 1.2
Multiply by 10, 100, 1000
Example : A box of crisps contain 48 packets.
How many in 100 boxes ?
48 x 100 =
4800
19-Apr-17
Created by Mr. Lafferty Maths Dept.

17. Whole Numbers www.mathsrevision.com Divide by 10, 100, 1000
National 4
NUM 1.2
Divide by 10, 100, 1000
Try and write down rule for 100, 1000
To Divide by 10, 100, 1000
To divide by 10 remove a zero from the number
To divide by 100 remove 2 zero’s from the number
To divide by 1000 remove 3 zero’s from the number
Example : Divide by 10, 100, 1000.
54000÷ 10 =
5400
54000 ÷ 100 =
540
54000 ÷ 1000 = 54
19-Apr-17
Created by Mr. Lafferty Maths Dept.

18. Created by Mr. Lafferty Maths Dept.
Whole Numbers
National 4
NUM 1.2
Divide by 10, 100, 1000
Example : A box contains 1000 cups. How many boxes are needed to hold 7000 ?
7000 ÷ 1000 = 7
19-Apr-17
Created by Mr. Lafferty Maths Dept.

19. Created by Mr. Lafferty Maths Dept.
Whole Numbers
National 4
NUM 1.2
Multiply & Divide by 10, 100, 1000
Now try
Exercise 4 & 5
Ch1 (page 11)
19-Apr-17
Created by Mr. Lafferty Maths Dept.

20. Created by Mr. Lafferty Maths Dept.
Starter Questions
National 4
NUM 1.2
36o
19-Apr-17
Created by Mr. Lafferty Maths Dept.

21. Created by Mr. Lafferty Maths Dept.
Whole Numbers
National 4
NUM 1.2
Multiply or Divide by 20,300,4000
Learning Intention
Success Criteria
1. Understand the two step process to multiply or divide by 20, 300 etc…
1. To explain how to divide by 20, 300, 4000 etc using our knowledge so far.
2. Show all working.
19-Apr-17
Created by Mr. Lafferty Maths Dept.

22. Whole Numbers www.mathsrevision.com
National 4
NUM 1.2
Multiply or Divide by 20,300,4000
By combining our knowledge so far of
“multiplying / dividing by 10, 100, 1000”
and
“multiplying / dividing by a single digit”
we can do harder calculations.
We use a TWO step process.
Example 1 : Calculate 20 x 52
20 can be written as 2 x 10 so we have :
2 x 10 x 52 =
Step 1 : 10 x 52 =
520
Step 2 : 2 x 520 =
1040
19-Apr-17
Created by Mr. Lafferty Maths Dept.

23. Created by Mr. Lafferty Maths Dept.
Whole Numbers
National 4
NUM 1.2
Multiply or Divide by 20,300,4000
Example 2 : Calculate 44 x 30
30 can be written as 10 x 3 so we have :
44 x 10 x 3 =
Step 1 : 44 x 10 =
440
Step 2 : 440 x 3 =
1320
Example 3 : Calculate 300 x 35
300 can be written as 3 x 100 so we have :
3 x 100 x 35 =
Step 1 : 100 x35 =
3500
Step 2 : 3500 x 3 =
10500
19-Apr-17
Created by Mr. Lafferty Maths Dept.

24. Created by Mr. Lafferty Maths Dept.
Whole Numbers
National 4
NUM 1.2
Multiply or Divide by 20,300,4000
Example 4 : Calculate ÷ 200
Since 200 divide by 100 then divide by 2:
16000 ÷ 100 ÷ 2 =
160
Step 1 : ÷ 100 = 80
Step 2 : 160 ÷ 2 =
19-Apr-17
Created by Mr. Lafferty Maths Dept.

25. Created by Mr. Lafferty Maths Dept.
Whole Numbers
National 4
NUM 1.2
Multiply or Divide by 20,300,4000
Example 5 : Calculate ÷ 6000
Since 6000 divide by 1000 then divide by 6:
÷ 1000 ÷ 6 =
120
Step 1 : ÷ = 20
Step 2 : 120 ÷ 6 =
19-Apr-17
Created by Mr. Lafferty Maths Dept.

26. Created by Mr. Lafferty Maths Dept.
Whole Numbers
National 4
NUM 1.2
Multiply or Divide by 20,300,4000
Now try Ex 6 & 7
Ch1 (page 12)
19-Apr-17
Created by Mr. Lafferty Maths Dept.