Solving the Equation: 0.3x + 7.4x = 3.8x - 3.5 + 1.4

Linear Equations with Decimal Coefficients

Solve for X:

0.3x4.5+7.4x=3.8x3.5+1.4 0.3x-4.5+7.4x=3.8x-3.5+1.4

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find X
00:05 Collect terms
00:16 Arrange the equation so that one side has only the unknown X
00:37 Collect terms
00:41 Isolate X
00:52 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 for X:

0.3x4.5+7.4x=3.8x3.5+1.4 0.3x-4.5+7.4x=3.8x-3.5+1.4

2

Step-by-step solution

To solve the equation 0.3x4.5+7.4x=3.8x3.5+1.4 0.3x - 4.5 + 7.4x = 3.8x - 3.5 + 1.4 , we will follow these steps:

  • Step 1: Simplify both sides of the equation by combining like terms.
  • Step 2: Isolate all terms involving x x on one side and constants on the other side of the equation.
  • Step 3: Solve for x x by dividing both sides by the coefficient of x x .

Let's work through each step:

Step 1: Simplify both sides of the equation.
On the left side, combine like terms: 0.3x+7.4x=7.7x 0.3x + 7.4x = 7.7x .
Thus, the equation becomes:

7.7x4.5=3.8x3.5+1.4 7.7x - 4.5 = 3.8x - 3.5 + 1.4

Simplify the right side:

3.8x3.5+1.4=3.8x2.1 3.8x - 3.5 + 1.4 = 3.8x - 2.1

The equation now is:

7.7x4.5=3.8x2.1 7.7x - 4.5 = 3.8x - 2.1

Step 2: Isolate the x x -terms on one side.
Subtract 3.8x 3.8x from both sides to get:

7.7x3.8x4.5=2.1 7.7x - 3.8x - 4.5 = -2.1

Which simplifies to:

3.9x4.5=2.1 3.9x - 4.5 = -2.1

Now, add 4.5 to both sides to isolate the x x -term:

3.9x=2.1+4.5 3.9x = -2.1 + 4.5

3.9x=2.4 3.9x = 2.4

Step 3: Solve for x x .
Divide both sides by 3.9:

x=2.43.9 x = \frac{2.4}{3.9}

x=0.6153846153... x = 0.6153846153...

Rounding to two decimal places, we find:

x=0.61 x = 0.61

Therefore, the solution to the problem is x=0.61 x = 0.61 .

3

Final Answer

0.61 0.61

Key Points to Remember

Essential concepts to master this topic
  • Combine Like Terms: Group all x-terms and all constants separately first
  • Technique: 0.3x+7.4x=7.7x 0.3x + 7.4x = 7.7x before moving terms across
  • Check: Substitute x=0.61 x = 0.61 : 7.7(0.61)4.5=0.197 7.7(0.61) - 4.5 = 0.197

Common Mistakes

Avoid these frequent errors
  • Moving terms before combining like terms
    Don't move 0.3x and 7.4x to opposite sides separately = creates unnecessary complexity and calculation errors! This leads to messy equations with more terms than needed. Always combine like terms on each side first, then move combined terms across the equals sign.

Practice Quiz

Test your knowledge with interactive questions

Solve for \( b \):

\( 8-b=6 \)

FAQ

Everything you need to know about this question

Why do I need to combine like terms first?

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Combining like terms simplifies the equation before you start moving things around. It's much easier to work with 7.7x 7.7x than juggling 0.3x 0.3x and 7.4x 7.4x separately!

What if I get confused with all these decimals?

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Take it one step at a time! Write down each step clearly and double-check your decimal arithmetic. You can also multiply everything by 10 to work with whole numbers if that helps.

How do I know which terms to move to which side?

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Move all x-terms to one side and all numbers to the other side. It doesn't matter which side you choose - just be consistent!

Why is my final answer a decimal and not a whole number?

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That's completely normal! Many real-world problems have decimal solutions. Just make sure to round appropriately (usually 2-3 decimal places) unless told otherwise.

How can I check if x = 0.61 is really correct?

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Substitute back into the original equation: 0.3(0.61)4.5+7.4(0.61)=3.8(0.61)3.5+1.4 0.3(0.61) - 4.5 + 7.4(0.61) = 3.8(0.61) - 3.5 + 1.4 . Both sides should equal 2.1 -2.1 !

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