maths smart grade 4 © 2012 alston publishing house pte ltd add mentally
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Maths Sm
art Grade 4 ©
2012 Alston Publishing House Pte LtdAdd mentally
Add mentallyM
aths Smart G
rade 4 © 2012 Alston Publishing H
ouse Pte Ltd
When we add numbers mentally, we are trying to find a quick way of adding the numbers in our heads.
Example:
Add 1473 and 206 mentally.
Maths Sm
art Grade 4 ©
2012 Alston Publishing House Pte LtdArea
Area is a measure of the amount of space inside a flat shape or figure.
AreaM
aths Smart G
rade 4 © 2012 Alston Publishing H
ouse Pte Ltd
Maths Sm
art Grade 4 ©
2012 Alston Publishing House Pte LtdCarroll diagram
Carroll diagramM
aths Smart G
rade 4 © 2012 Alston Publishing H
ouse Pte Ltd
A Carroll diagram helps us sort data in a ‘yes’ or ‘no’ manner. A simple Carroll diagram has two groups.
If the first group is labelled ‘A’, then the second group is usually labelled ‘Not A’.
We can further sort the data in the two groups into two more groups to get four groups as shown.
Carroll diagramM
aths Smart G
rade 4 © 2012 Alston Publishing H
ouse Pte Ltd
Example:
or
This Carroll diagram sorts the animals according to whether they are owls and whether they are brown.
Maths Sm
art Grade 4 ©
2012 Alston Publishing House Pte LtdCount back
Count backM
aths Smart G
rade 4 © 2012 Alston Publishing H
ouse Pte Ltd
Counting down from a bigger number to a smaller number.
Example: To get from 6231 to 4000, we count back in thousands first, then hundreds, tens and finally ones.
Maths Sm
art Grade 4 ©
2012 Alston Publishing House Pte LtdCount on
Count onM
aths Smart G
rade 4 © 2012 Alston Publishing H
ouse Pte Ltd
Counting up from a smaller number to a bigger number.
Example: To get from 3787 to 6000, we count on in thousands first, then hundreds, tens and finally ones.
Maths Sm
art Grade 4 ©
2012 Alston Publishing House Pte LtdDecimal
DecimalM
aths Smart G
rade 4 © 2012 Alston Publishing H
ouse Pte Ltd
A fraction can be written as a decimal. A decimal has a whole number part and a fraction part that is separated by a decimal point.
Example:
65.27 is a decimal number.
Maths Sm
art Grade 4 ©
2012 Alston Publishing House Pte LtdDecimal point
Decimal pointM
aths Smart G
rade 4 © 2012 Alston Publishing H
ouse Pte Ltd
A decimal point separates the whole number part from the fraction part of the number.
Example:
Maths Sm
art Grade 4 ©
2012 Alston Publishing House Pte LtdDouble
DoubleM
aths Smart G
rade 4 © 2012 Alston Publishing H
ouse Pte Ltd
When we find the double of a number, we add the number to itself.
Example:
Double 2550.
So, double 2550 is 5100.
Maths Sm
art Grade 4 ©
2012 Alston Publishing House Pte LtdDuration
DurationM
aths Smart G
rade 4 © 2012 Alston Publishing H
ouse Pte Ltd
The amount of time an event lasts for (between starting time and ending time).
Example:
A cooking class started at 3.30 p.m. and ended at 5.30 p.m. What was the duration of the cooking class?
The duration of the cooking class was 2 h.
Maths Sm
art Grade 4 ©
2012 Alston Publishing House Pte LtdHalf
HalfM
aths Smart G
rade 4 © 2012 Alston Publishing H
ouse Pte Ltd
When we find half of a number, we divide the number by 2.
Example:
Half of 6700.
So, half of 6700 is 3350.
Maths Sm
art Grade 4 ©
2012 Alston Publishing House Pte LtdHundredth
HundredthM
aths Smart G
rade 4 © 2012 Alston Publishing H
ouse Pte Ltd
When we divide one whole into 100 equal parts, each part is one hundredth of the whole.
Example:
(1 hundredth) = 0.011001
Maths Sm
art Grade 4 ©
2012 Alston Publishing House Pte Ltd
Improper fraction
Improper fractionM
aths Smart G
rade 4 © 2012 Alston Publishing H
ouse Pte Ltd
An improper fraction has a numerator that is greater than or equal to its denominator. The value of an improper fraction is equal to or greater than 1.
Example:
The improper fraction represented by the shaded partsis .34
Maths Sm
art Grade 4 ©
2012 Alston Publishing House Pte LtdMillimetre (mm)
Millimetre (mm)M
aths Smart G
rade 4 © 2012 Alston Publishing H
ouse Pte Ltd
A unit of measurement for length.
Example:
The length of the nail is 18 millimetres (or 18 mm).
Maths Sm
art Grade 4 ©
2012 Alston Publishing House Pte LtdMixed number
Mixed numberM
aths Smart G
rade 4 © 2012 Alston Publishing H
ouse Pte Ltd
A mixed number is made up of a whole number and a fraction. The value of a mixed number is always greater than 1.
Example:
The mixed number represented by the shaded parts is .
431
Maths Sm
art Grade 4 ©
2012 Alston Publishing House Pte Ltd
Multiply mentally
Multiply mentallyM
aths Smart G
rade 4 © 2012 Alston Publishing H
ouse Pte Ltd
When we multiply numbers mentally, we are trying to find a quick way of multiplying the numbers in our heads.
Example:
Multiply 6 and 30 mentally.
Maths Sm
art Grade 4 ©
2012 Alston Publishing House Pte LtdPerimeter
PerimeterM
aths Smart G
rade 4 © 2012 Alston Publishing H
ouse Pte Ltd
The perimeter of a figure is the total distance around all the sides of the figure.
Example:
The perimeter of the rectangle is 14 cm.
Maths Sm
art Grade 4 ©
2012 Alston Publishing House Pte LtdProper fraction
Proper fractionM
aths Smart G
rade 4 © 2012 Alston Publishing H
ouse Pte Ltd
A proper fraction has a numerator that is smaller than its denominator. The value of a proper fraction is between 0 and 1.
Example:
The proper fraction represented by the shaded part is .31
Maths Sm
art Grade 4 ©
2012 Alston Publishing House Pte Ltd
Round to the nearest tenth
Round to the nearest tenthM
aths Smart G
rade 4 © 2012 Alston Publishing H
ouse Pte Ltd
When we round a number to the nearest tenth, we look at the digit in the hundredths place.(a)If the digit < 5, we round it to the smaller tenth.(b)If the digit > 5, we round it to the bigger tenth.(c)If the digit = 5, we round it to the bigger tenth.
Maths Sm
art Grade 4 ©
2012 Alston Publishing House Pte Ltd
Round to 1 decimal place
Round to 1 decimal placeM
aths Smart G
rade 4 © 2012 Alston Publishing H
ouse Pte Ltd
Rounding to 1 decimal place is the same as rounding to the nearest tenth.
Maths Sm
art Grade 4 ©
2012 Alston Publishing House Pte Ltd
Round to the nearest whole
number
Round to the nearest whole numberM
aths Smart G
rade 4 © 2012 Alston Publishing H
ouse Pte Ltd
When we round a number to the nearest whole number, we look at the digit in the tenths place.(a)If the digit < 5, we round it to the smaller wholenumber.(b)If the digit > 5, we round it to the bigger whole number.(c)If the digit = 5, we round it to the bigger whole number.
Maths Sm
art Grade 4 ©
2012 Alston Publishing House Pte Ltd
Square centimetre (cm2)
Square centimetre (cm2)M
aths Smart G
rade 4 © 2012 Alston Publishing H
ouse Pte Ltd
A unit of measurement for area.
Example:
The area of the square is 1 square centimetre (or 1 cm2).
Maths Sm
art Grade 4 ©
2012 Alston Publishing House Pte Ltd
Square metre (m2)
Square metre (m2)M
aths Smart G
rade 4 © 2012 Alston Publishing H
ouse Pte Ltd
A unit of measurement for area.
Example:
The area of the square is 1 square metre (or 1 m2).
Maths Sm
art Grade 4 ©
2012 Alston Publishing House Pte LtdSquare unit
Square unitM
aths Smart G
rade 4 © 2012 Alston Publishing H
ouse Pte Ltd
A unit of measurement for area.
Example:
The area of the figure is 6 square units.
Maths Sm
art Grade 4 ©
2012 Alston Publishing House Pte Ltd
Subtract mentally
Subtract mentallyM
aths Smart G
rade 4 © 2012 Alston Publishing H
ouse Pte Ltd
When we subtract numbers mentally, we are trying to find a quick way of subtracting the numbers in our heads.
Example:
Subtract 302 from 8348 mentally.
Maths Sm
art Grade 4 ©
2012 Alston Publishing House Pte LtdTenth
TenthM
aths Smart G
rade 4 © 2012 Alston Publishing H
ouse Pte Ltd
When we divide one whole into 10 equal parts, each part is one tenth of the whole.
Example:
(1 tenth) = 0.1101
Maths Sm
art Grade 4 ©
2012 Alston Publishing House Pte LtdTime line
Time lineM
aths Smart G
rade 4 © 2012 Alston Publishing H
ouse Pte Ltd
We use a time line to help us calculate duration.
Example:
Ari’s birthday party began at 11.30 a.m. and ended at 2.50 p.m. The duration of the party was 3 h 20 min.
Maths Sm
art Grade 4 ©
2012 Alston Publishing House Pte LtdVenn diagram
Venn diagramM
aths Smart G
rade 4 © 2012 Alston Publishing H
ouse Pte Ltd
A Venn diagram uses circles to help us sort data into different groups.
Example:
This Venn diagram sorts the data according to whether they are multiples of 2, multiples of 5 and/or two-digit numbers.