Adding and subtracting integers, some answers are positive and others negative. How can you tell which answers will be positive and which negative?Remember I need drastic explanation. I do not...

Adding and subtracting integers, some answers are positive and others negative. How can you tell which answers will be positive and which negative?

Remember I need drastic explanation. I do not understand maths very well.

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malkaam's profile pic

malkaam | Student, Undergraduate | (Level 1) Valedictorian

Posted on

Here are some important points related to signs:

  • Two same signs result in addition and the sign of the bigger number is taken.
  • Two different signs result in subtraction and the sign of the bigger number is taken.
  • When multiplying or dividing signs are also multiplied such that, + * - = -

                                                                                                  + * + = +

                                                                                                   - * - = +

                                                                                                   - * + = -

i.e. different signs when multiplied become negative, same signs when multiplied become positive.  

neela's profile pic

neela | High School Teacher | (Level 3) Valedictorian

Posted on

The addition and subtraction are the basis of counting. Try these examles. Before that we must know that an absolte of a number is the postive value of the number irrespective of the sign of the number.

5+10=15.

10+20=30

(-5)+(-10)= -15 or

-5-10 = -15

-10-20 =-30.

Thus the addition of two numbers with the same sign is adding them absolutely and retaining the common sign.

Below  here the two number are  of different signs. See how they are simplified:

10-20 = -10

-30+45 = 15 or +15.

So when two numbers are of diffrent  signs find their diffrence and put the sign of the absolutely bigger number. This may go on for some time and you need some practice. Hope the best.

 

 

krishna-agrawala's profile pic

krishna-agrawala | College Teacher | (Level 3) Valedictorian

Posted on

Whenever you are adding or subtracting just two numbers you can follow these simple rules.

  1. First change the sign of the number to be subtracted.That is change +ve to -ve, and -ve to positive. If the numbers are to be added there is no need to change the sign.
  2. After the signs have changed as given above there are two possibilities. (1) both the numbers have same signs, or (2) the two numbers have different sign. If both the signs are same add the two numbers and give the common sign of the two numbers to the result. If the signs are opposite subtract the smaller number from the bigger number and give the sign of bigger number to the result.

If you have more than two numbers it is best to change the signs of numbers as suggested i step (1) above, then add separately numbers with +ve and -ve signs, and assign respective signs to the respective sum. This will reduce the problem to a two number problem with opposite signs. If all the terms after sign conversion are of the same signs, then you add all the terms together and assign the common sign to the result, which gives you the final result.

Please note that frequently the +ve sign is not always shown before a +ve number. So a number without a sign is assumed to be positive.

Also at times you may be given just a series of number with signs, Without any instruction of what is to be subtracted from what. In this case sign conversion as in step (1) above is not necessary and you can proceed straight to subsequent steps.

Please note that these rules or method can be applied to integers as well as fractions.

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