Solve the Ratio Equation: Find Proportion Between (3a-12b) and (9x/4y)

Division by Fractions with Algebraic Expressions

(3a12b):(9x/4y)=? (3a-12b):(9x/4y)=\text{?}

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Solve
00:07 Write division as a fraction
00:15 Division is also multiplication by the reciprocal
00:30 Take out 3 from the parentheses
00:41 Factor 9 into 3 and 3
00:49 Reduce what's possible
00:56 Be sure to multiply numerator by numerator and denominator by denominator
01:01 Open the parentheses properly
01:07 The outer factor will multiply each factor in parentheses
01:14 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

(3a12b):(9x/4y)=? (3a-12b):(9x/4y)=\text{?}

2

Step-by-step solution

To solve the mathematical expression (3a12b):(9x/4y) (3a-12b):(9x/4y) , follow these steps:

  • Step 1: Understand that the notation (3a12b):(9x/4y) (3a-12b):(9x/4y) means (3a12b)÷(9x4y)(3a-12b) \div \left( \frac{9x}{4y} \right).
  • Step 2: Migrate from division to multiplication by taking the reciprocal of the divisor: (3a12b)×(4y9x)(3a-12b) \times \left( \frac{4y}{9x} \right).
  • Step 3: Apply the distributive property:

Multiply (3a12b) (3a-12b) by 4y9x \frac{4y}{9x} :

(3a×4y9x)+(12b×4y9x)=3a×4y9x12b×4y9x (3a \times \frac{4y}{9x}) + (-12b \times \frac{4y}{9x}) = \frac{3a \times 4y}{9x} - \frac{12b \times 4y}{9x}

Simplify each term:

  • First term: 3a×4y9x=12ay9x=4ay3x\frac{3a \times 4y}{9x} = \frac{12ay}{9x} = \frac{4ay}{3x}
  • Second term: 12b×4y9x=48by9x=16by3x\frac{12b \times 4y}{9x} = \frac{48by}{9x} = \frac{16by}{3x}

Thus, the expression becomes:

4ay3x16by3x=4ay16by3x\frac{4ay}{3x} - \frac{16by}{3x} = \frac{4ay - 16by}{3x}

Therefore, the solution to the problem is 4ay16by3x \frac{4ay-16by}{3x} .

3

Final Answer

4ay16by3x \frac{4ay-16by}{3x}

Key Points to Remember

Essential concepts to master this topic
  • Rule: Division by a fraction equals multiplication by its reciprocal
  • Technique: Convert ÷9x4y \div \frac{9x}{4y} to ×4y9x \times \frac{4y}{9x}
  • Check: Verify distributive property: both terms multiplied by same fraction ✓

Common Mistakes

Avoid these frequent errors
  • Treating the colon as a regular ratio instead of division
    Don't write (3a-12b):(9x/4y) as a simple ratio = missing the division operation! The colon here means division, not comparison. Always convert the colon notation to division first, then apply the reciprocal rule.

Practice Quiz

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\( 100-(30-21)= \)

FAQ

Everything you need to know about this question

What does the colon (:) mean in this expression?

+

The colon (:) represents division, not a ratio comparison. So (3a12b):(9x/4y) (3a-12b):(9x/4y) means (3a12b)÷9x4y (3a-12b) \div \frac{9x}{4y} .

Why do I flip the fraction when dividing?

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Dividing by a fraction is the same as multiplying by its reciprocal. This rule makes division easier to calculate and ensures you get the correct result.

Do I need to distribute to both terms in the parentheses?

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Yes! When multiplying (3a12b) (3a-12b) by 4y9x \frac{4y}{9x} , you must multiply both 3a and -12b by the fraction.

How do I simplify fractions with variables?

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Look for common factors in numerator and denominator. For example, 12ay9x=4ay3x \frac{12ay}{9x} = \frac{4ay}{3x} by dividing both parts by 3.

Can I combine the fractions at the end?

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Only if they have the same denominator! Since both terms have denominator 3x, you can write 4ay3x16by3x=4ay16by3x \frac{4ay}{3x} - \frac{16by}{3x} = \frac{4ay-16by}{3x} .

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