1. Adding and Subtracting integers - word problems

2. Integers Recap
Zero
Negative integers
Positive integers
The numbers –1, –2, –3, … (to the left of zero) are called negative integers
The numbers 1, 2, 3,… (to the right of zero) as positive integers.
The new set of numbers …, -3, -2, -1, 0, 1, 2, 3,… are called Integers.
‘–’ symbol in front of a number is read as 'negative' or 'minus'.
For example, –5 is read as negative 5 or minus 5.
A number without a sign is considered as a positive number.
For example, 5 is considered as +5.

3. Terminologies Positive Negative Above sea level Above ground Increase
Gain/Profit
Deposit
Positive Marking
Kept back
Raises
Below sea level
Below ground
Decrease
Loss
Withdraw
Negative Marking
Taken Out
Descends

4. + ( + ) = + + ( - ) = - - ( - ) = + - ( + ) = -
Rules of Addition and subtraction
Rule 1
Two numbers have same sign
Add the numbers
Copy bigger number sign
Rule 2
Two numbers have different sign
Subtract the numbers
Copy bigger number sign
Rules of multiplication
Converting 2 symbols into 1
Rule 1
Multiply same sign  Answer is +
+ ( + ) = +
- ( - ) = +
Rule 2
Multiply different sign Answer is –
+ ( - ) = -
- ( + ) = -

5. Answer: Current location is – 735ft
Example 1: A submarine descends ft below sea level . It rises 465 ft. Where it
is currently located ?
To find: Current location of submarine
Solution:
submarine descends
1200 ft below sea level (From A to B) = ft
Submarine Raises 465 ft (From B to C) = ft
Therefore current location (D) = A to B + B to C = =
= -735 ft
= ft
Sea level A C
1200 ft below
sea level
= ft
Raises
465 ft
= + 465 B B
By addition rule 2
Answer: Current location is – 735ft

6. Answer: Number of books in the library = 516
Example 2 : There are 600 books in the library. On Monday 124 books are taken out
on Tuesday 49 books are taken out , and on Wednesday 89 books are brought back,
find how many books are there in library now ?
Given: Total Number of books = 600
Solution:
No of books taken out in Monday is = -124
No of books taken out in Tuesday is = - 49
No of books Kept back in Wednesday is 89 = +89
Number of book in library = A - B + C =
= –
= – 173 = 516 books
100 books
100 books
100 books
100 books
100 books
100 books A
124 taken out = - 124 B
49 taken out = - 49 C
89 kept back = + 89
By addition rule 1
Answer: Number of books in the library = 516
By addition rule 2

7. Try these
There are 154 lions, 77 tigers and 132 cheetahs in a forest. Out of which 30 each of all 3 categories are being sent to a zoo. How many animals will be left in the forest ?
Mohan deposits Rs 2000 in his bank account on the first day and Rs 3000 on the second day. He withdraws Rs 4000 on the third day. How much money does he have at the end of the third day ?