Solve Addition Expression: (+8) + (-4.5) Step by Step

Adding Integers with Negative Decimals

Solve the following expression:

(+8)+(4.5)= ? (+8)+(-4.5)=\text{ ?}

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Solve
00:03 Find point (8) on the axis
00:08 Positive times negative always equals negative, so we subtract
00:12 To subtract, we move in the left (negative) direction on the axis
00:19 Let's calculate
00:23 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Solve the following expression:

(+8)+(4.5)= ? (+8)+(-4.5)=\text{ ?}

2

Step-by-step solution

First we need to locate the number 8 on the number line and move 4.5 steps to the left from it:

000888

Remember the rule:

+(x)=x +(-x)=-x

Now let's rewrite the problem in the appropriate form and solve:

84.5=3.5 8-4.5=3.5

3

Final Answer

3.5 3.5

Key Points to Remember

Essential concepts to master this topic
  • Rule: Adding a negative number means subtracting its absolute value
  • Technique: Rewrite (+8) + (-4.5) as 8 - 4.5 = 3.5
  • Check: Start at 8, move left 4.5 units to reach 3.5 ✓

Common Mistakes

Avoid these frequent errors
  • Adding the absolute values instead of subtracting
    Don't add 8 + 4.5 = 12.5 when you see (+8) + (-4.5)! The negative sign means subtraction, not addition. Always recognize that adding a negative number is the same as subtracting the positive version.

Practice Quiz

Test your knowledge with interactive questions

a is negative number.

b is negative number.

What is the sum of a+b?

FAQ

Everything you need to know about this question

Why does adding a negative number mean subtracting?

+

Think of it as moving on a number line. Adding moves you right, but a negative number means you move in the opposite direction - left! So (+8) + (-4.5) means start at 8 and move 4.5 units left.

How do I know whether my answer should be positive or negative?

+

Look at which number has the larger absolute value. Since 8 > 4.5, and 8 is positive, your answer will be positive. The sign follows the larger number!

What's the difference between (+8) + (-4.5) and (-8) + (+4.5)?

+

The first gives you 3.5 (positive), while the second gives you -3.5 (negative). The order matters because you're starting from different positions on the number line!

Can I just ignore the parentheses around the numbers?

+

Never ignore them! The parentheses show you the sign of each number clearly. (+8) means positive 8, and (-4.5) means negative 4.5. They prevent confusion about which signs go with which numbers.

How can I check my answer using the number line?

+

Start at your first number (8), then move according to your second number. Since it's -4.5, move 4.5 units to the left. You should land on 3.5!

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