What are integers?

An integer is a whole number from the set of negative, non-

negative, and positive numbers. To be an integer, a number

cannot be a decimal or a fraction.

Integers

• Any number that is positive (+) is always what you have.

• Any number that is negative (-) is always what you owe.

Have (+)

Have (+)

Owe (-)

Number Line

Number Line Rules

1. When we are subtracting we move to the (direction) LEFT

2. When we are adding we move to the (direction) RIGHT

Addition of integers

-2 + 4

-2 is what
you owe

4 is what
you have

When you owe (-2)
dollars and you paid
Mr. Chin $4 (have) ,
ARE YOU GOING TO
OWE MR. CHIN?

EXPLAIN!!!

Subtraction of integers

-6 - 3

-6 is was
you owe

3 becomes
-3 because
of the minus
sign. You
owe (-3)

If you owe $(-6)
and go back and
owe $(-3), What’s
the total of what
you owe?

Explain!!!

Multiplication

Of

INTEGERS

{positive × positive = positive}

a×b= ab

2×4=?

2

4

8

{negative × positive = negative}

-a×b= -ab

-2×8=?

Evaluate 3×-4= ?

-2

8
-16

{negative × negative = positive}

-a×-b= ab

-2×-9=?

-5×-4= ?

-2

-9
18

LET’S DO SOME MATHS

Practice

❏ -12×3=

❏ -6×-6=

❏ -2×4×-6=

❏ 7 (2+1)=

Division

Of

Integers

{negative ÷ positive = negative}

-a÷b= -ab

-12÷3=?

36 ÷ -6= ?

-12

3
-4

{negative ÷ negative = positive}

-a ÷ -b= ab

-27 ÷ -9=?

-45 ÷ -5= ?

-27

-9
3

{positive ÷ positive = positive}

a÷b= ab

22÷11=?

22

11

2

36÷3= ?

SUMMARY

{positive x positive = positive} (+) x (+) = (+)

{negative x positive = negative} (-) x (+) = (-)

{negative x negative = positive} (-) x (-) = (+)

{positive ÷ positive = positive}

{negative ÷ positive = negative}

{negative ÷ negative = positive}

Worded
Problems

• The cost of a comic book is $620 and the cost of a pack of

crayons is $1140. Calculate the total cost of the purchases.

Comic book = $620

Pack of crayons = $1140

620 + 1140 =?

• I had a piece of string 300 cm in length. I cut off three pieces, one

of length 97cm, one of length 53cm and one of length 112cm.

What is the length of the piece of string that I had left?

•A man is paid $525 for working a 5-day week. What amount does

he get paid per day?

• The contents of a tin of sweets had a mass of 5000

grams. The sweets are divided into packets each of

mass 250g. How many packets of sweets can be

made?

• On Monday, 1500 hamburgers were cooked in a school canteen.

At first sitting, 357 hamburgers were served. At the second sitting,

655 hamburgers were served. At the third sitting, 421 hamburgers

were served. How many hamburgers were left after the three

sitting?