LESSON 2
• To arrange numbers in ascending
order, means to place them from
smallest (first) to largest (last).
Example:
Place 3, 1, 19, 12, 9, 2 and 7 in
ascending order.
Answer: 1, 2, 3, 7, 9, 12, 19
• Descending order of numbers
refers to arranging numbers in
decreasing order, from the
largest(first) to the smallest (last).
Example:
Place 17, 5, 9 and 8 in descending
order.
Answer: 17, 9, 8, 5
For large numbers or numbers close in value:
• Firstly compare the number of digits in
each number (draw a place value chart
to line the numbers up)
• The whole number with lesser digits is
the smallest number
• The whole number with the largest
digits is the largest number
• If the number of digits is the same, then
compare the left-most digits of the
numbers
• If you have decimal numbers with the
same whole number parts, then compare
the decimal fractions.
Remember decimals get smaller to the right!
Practice questions:
ESTIMATE AND ROUNDING OFF
• To make calculations easier and more
realistic, an estimate of a number is a
reasonable guess of the actual value.
• Approximating a quantity to nearest
accurate value is what estimation is all
about.
• This is obtained by rounding off the
numbers in the calculation and
obtaining a quick and approximate
answer.
Rounding-off
• Rounding off is nothing but
estimation. Estimating the actual
number to its nearby number is
called rounding off.
• Except, you are told which place
value to round off your number
to.
• Note: numbers can be rounded
up or down.
• When someone asks you the
price of your book, you say 100
even if it is 98. This is giving an
estimation after rounding off a
number. This is how we apply
the concept of rounding off in
our everyday life.
How to “round off” whole numbers?
How to “round off” decimal numbers?
Step 1
Identify and underline the digit in
the ones place.
Example: 12.543
Step 2
Look at the digit directly after the
decimal point.
Example: 12.543
Step 3
If it is 5 or above, add 1 to the
underlined digit.
If it is less than 5, leave the
underlined digit the same.
Example: 12+1= 13.543
Step 4
Drop the decimal point and all the
digits after the underlined number.
Example: 13.543 = 13
Check out this Youtube video!
Practice questions:
Addition
• The sum of two or more numbers
is called addition.
• Commutative law can be applied.
• This law states that the result for
addition will be the same even
when the order of the numbers
changes.
Subtraction
• Subtraction is taking one number
or amount away from another.
• The result is called the difference
of both numbers.
Multiplication
• Multiplication is repeated
addition.
• Commutative law can be
applied.
• This law states that if two or
more numbers are multiplied
the product will be the same
no matter their order
Division
• Division can be represented by
grouping or partitioning.
• It means to find out how many
groups of a number can fit into
another number.
• Zero divided by any number
equals zero. Example:
• Any number divided by itself
equals 1, except the number 0.
Example:
Practice questions: