Arithmetic of Computers

Arithmetic of Computers

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Lesson 3

Negative Numbers

Real values of less than nothing

Page 117

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Your answer :
( − 5) + ( − 8) = ( − 13).
You are correct. Very good.
Now, adding numbers with the same signs causes no problem. But what if we need to add two numbers that have different signs, one positive and one negative? The rule here is: To add numbers of unlike signs find the difference of the absolute values and use the sign of the number with the larger absolute value.
Thus, if we have the problem ( − 3) + ( + 2), the absolute values are 3 and 2, the difference (found by subtracting one absolute value from the other) is 1, and the sign of the number with the larger absolute value was -, so ( − 3) + ( + 2) =  − 1.
In the problem ( + 7) + ( − 4), the difference of the absolute values is 3, and the sign of the number with the larger absolute value is +, so
( + 7) + ( − 4) = ( + 3).
Study the following examples:
( − 8) + ( + 5)  =  − 3,  ( + 6) + ( − 7)  =  − 1,  ( + 7) + ( − 6)  =  + 1,  ( + 10) + ( − 14)  =  − 4,  ( + 14) + ( − 10)  =  + 4, 
and so on.
Very well, pick the one correct equation below.
Answer :
( − 9) + ( + 6) = ( − 3).

Go to Page 108

( − 9) + ( + 6) = ( − 15).

Go to Page 113


Answer to Self-Test Question 4, Lesson 3 :
 − 7 + 5 =  − 2.

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