Rounding

1
Rounding

• Understand how to round numbers to the nearest
  10, whole number or decimal place.

2
Starter order decimals

• Which value is the bigger?

4.17km
0.84
0.325
0.345
0.72
11.7
7.30cm
11.57
7.03cm
4.162km
3
Starter order decimals

• Put these in order, smallest first.

0.231
0.213
0.132
0.123
0.312
4
What is the value
3 4 5
5
Round the following number to 1dp
Now look at the number immediately after where we
stopped highlighting
If this number is a 0, 1, 2, 3 or 4 we dont have
to do anything else and we have our answer.

• 6.348

Firstly, highlight the number to the first number
after the decimal point
So we have 6.3 But is this the answer?
6
Round the following number to 1dp

• 6.348 6.3 (1dp)

7
What if the red number was a 5, 6, 7, 8 or 9?

• Lets look at an example

8
Round the following number to 1dp
Now look at the number immediately after where we
stopped highlighting
If this number is a 5, 6, 7, 8 or 9 we increase
the last digit by one.

• 9.2721

Firstly, highlight the number to the first number
after the decimal point
So we have 9.2 But is this the answer?
So 9.2 becomes 9.3
9
Round the following number to 1dp

• 9.2721 9.3 (1dp)

10
Roundingto the nearest whole number

• Is the arrow nearer to 6, 7 or 8?
• If it is halfway between, then round UP

6 7 8
11
Round these city populations to the nearest
million

• Mexico City 21.5 million
• Sao Paulo 19.9 million
• Tokyo 19.5 million
• New York 15.7 million

12
Roundingto the nearest 10

• Is the arrow nearer to 20, 30 or 40?
• If it is halfway between, then round UP

20 30 40
13
What is the volume of liquid to the nearest 10
millilitres
14
Roundingto the nearest 100

• Is the arrow nearer to 400 or 500?
• If it is halfway between, then round UP

400 500
15
What is the mass of flour to the nearest 100g?

• Estimate the value to the nearest 10g

16
Rounding to 1 decimal place

• What value is the arrow pointing at?
• Is it nearer to 1.4 or 1.5?

1.4 1.5
17
Rounding heights distances

• Round each of these winning heights distances
  to the nearest whole number
• Round them to one decimal place (1 d.p.)

18
Take Care!

• Round 3.48 to 1 d.p

3.5

• Round 3.48 to the nearest whole number

3 (not 4)