DECIMAL NUMBERS
10 of 0.1 is adding of 10 0.1s = 1
0.1
+ 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 +0.1 + 0.1 = 1.0
10
tenths = 1 one
DECIMAL NUMBERS: ADDITION
Example
Add 7.3 and 14.5
Method
Step1: Line numbers using the decimal point
7.3
+14.52
Step2:
7.30
+14.52
Step3: Add
7.30
+14.52
21.82
<<Filling The Decimal Number With Zero - 12.5 is the same as 12.50 or 12.500
The zero can be used to show rounding digit>>
12.5
is the same as 12.50 or 12.500
Example
Add 237 and 8.42 and 25.8
Method
Step1: Line
the number using the decimal point
237
8.42
+25.8
Step2: ‘Fill’ zero to equal decimal place
237.00
8.42
+25.80
Step3: Add
237.00
8.42
+25.80
271.22
ESTIMATE
Example
Add 6.3 and 12.6
Method
Step1: Line
the number using the decimal point
6.3
+12.8
Step2: ‘Fill’ zero to equal decimal place
6.3
+12.8
Step3: Add
6.3
+12.8
19.1
<< Estimate: To Check If the Answer Is Reasonable >>
Step1: Round off
each number
6.3 = 6, 12.8 = 13.
Step2: Add the
numbers
6 + 13 = 19
Step3: Compare the
number.
The difference is 0.1. The answer is
reasonable.
DECIMALS: SUBTRACTION
Example
Subtract 1.5 from 8.73
Method
Step1: Line
the number using the decimal point
8.73
-1.5
Step2: ‘Fill’ zero to equal decimal place
8.73
-1.50
Step3: Subtract
8.73
-1.50
7.23
Word Problems
Example (1)
Dave and Sally have
a total mass of 82.15 kg. Sally’s mass is 39.6. What is Dave’s mass?
Step1:
Underline keywords and list objects
Sally Dave
Step2: Draw Model
Step3: Solve
Step1:
Align Decimal point
82.15
- 39.60
Step2:
‘Fill’ zero to equal decimal place
82.15
- 39.60
Step3:
Subtract
82.15
-39.60
43.55
Dave’s mass is 43.55
kg
Example (2)
Amy jogged a
distance of 2.6km and walked a distance of 1.25 km. What was the total distance
that Amy covered?
Step1: Underline keywords and list objects
Amy
Step2: Draw Model and link numbers
Step3: Solve
Step1:
Align Decimal point
2.6
+ 1.25
Step2:
‘Fill’ zero to equal decimal place
2.60
+ 1.25
Step3:
Subtract
2.60
+ 1.25
3.85
km
Amy covered a
distance of 3.85 km
