When adding a long string of positives and negatives, such as $(-4)+(+9)+(+4)+(-2)$, there are two very common approaches:

Method 1: Find the sum of all the positives, then find the sum of all the negatives, and then add the two answers together.
Method 2: Find all the number pairs whose sum is zero. Then add whatever is left over.

Both methods work, but depending on the numbers involved sometimes one method is easier than the other.

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Example 1: $(-4)+(+9)+(+4)+(-2)=$

Method 1: Collecting "like" signs

Method 2: Collecting "opposite" signs

Example 1a

Example 1b

Example 2: $(+3)+(-5)+(-9)+(+5)+(-3)=$

Method 1: Collecting "like" signs

Method 2: Collecting "opposite" signs

Example 2a

Example 2b

Self-Check

Question 1

Find the sum:

$(-3)+(-7)+(+4)+(+7)+(+3)=$

Question 2

Find the sum:

$(+13)+(-4)+(+7)+(-13)=$

Question 3

Find the sum:

$(-4)+(+9)+(+2)+(-5)=$

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