 Addition of Numbers with Like Signs
 Addition with Zero
 Addition of Numbers with Unlike Signs
 Calculators
Inside Collection (Textbook): Derived copy of Fundamentals of Mathematics
Summary: This module is from Fundamentals of Mathematics by Denny Burzynski and Wade Ellis, Jr. This module discusses how to add signed numbers. By the end of the module students should be able to add numbers with like signs and with unlike signs and be able to use the calculator for addition of signed numbers.
The addition of the two positive numbers 2 and 3 is performed on the number line as follows.
Begin at 0, the origin.
Since 2 is positive, move 2 units to the right.
Since 3 is positive, move 3 more units to the right.
We are now located at 5.
Thus,
Summarizing, we have
The addition of the two negative numbers 2 and 3 is performed on the number line as follows.
Begin at 0, the origin.
Since 2 is negative, move 2 units to the left.
Since 3 is negative, move 3 more units to the left.
We are now located at 5.
Thus,
Summarizing, we have
Observing these two examples, we can suggest these relationships:
Addition of numbers with like sign:
To add two real numbers that have the same sign, add the absolute values of the numbers and associate with the sum the common sign.
Find the sums.
The common sign is “+.”
Thus,
The common sign is “
Thus,
Find the sums.
14
52
12
45
34
Notice that
Since adding zero to a real number leaves that number unchanged, zero is called the additive identity.
The addition
Begin at 0, the origin.
Since 2 is positive, move 2 units to the right.
Since 6 is negative, move, from 2, 6 units to the left.
We are now located at 4.
We can suggest a rule for adding two numbers that have unlike signs by noting that if the signs are disregarded, 4 can be obtained by subtracting 2 from 6. But 2 and 6 are precisely the absolute values of 2 and 6. Also, notice that the sign of the number with the larger absolute value is negative and that the sign of the resulting sum is negative.
Addition of numbers with unlike signs: To add two real numbers that have unlike signs, subtract the smaller absolute value from the larger absolute value and associate with this difference the sign of the number with the larger absolute value.
Find the following sums.
Subtract absolute values:
Attach the proper sign: "+."
Thus,
Subtract absolute values:
Attach the proper sign: "
Thus,
The morning temperature on a winter's day in Lake Tahoe was 12 degrees. The afternoon temperature was 25 degrees warmer. What was the afternoon temperature?
We need to find
Subtract absolute values:
Attach the proper sign: "+."
Thus,
Find the sums.
1
2
3
6
14
43
5
0.5
8
0.57
425
Calculators having the key can be used for finding sums of signed numbers.
Use a calculator to find the sum of 147 and 84.
Display Reads  
Type  147  147  
Press  147  This key changes the sign of a number. It is different than 

Press  +  147  
Type  84  84  
Press  =  63 
Use a calculator to find each sum.
48
6,085
7,993.7
Find the sums in the following 27 problems. If possible, use a calculator to check each result.
16
15
8
25
12
24
21
0
0
23
328
876
1,255
6.084
In order for a small business to break even on a project, it must have sales of $21,000. If the amount of sales was $15,000, by how much money did this company fall short?
Suppose a person has $56 in his checking account. He deposits $100 into his checking account by using the automatic teller machine. He then writes a check for $84.50. If an error causes the deposit not to be listed into this person’s account, what is this person’s checking balance?
$28.50
A person borrows $7 on Monday and then $12 on Tuesday. How much has this person borrowed?
A person borrows $11 on Monday and then pays back $8 on Tuesday. How much does this person owe?
$3.00
((Reference)) Find the reciprocal of
((Reference)) Find the value of
((Reference)) Round 0.01628 to the nearest tenth.
((Reference)) Convert 62% to a fraction.
((Reference)) Find the value of
"Used as supplemental materials for developmental math courses."