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Finding the Fourth Proportional to 85.72, 128.76 and 45.13

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Solution

The fourth proportional to 85.72, 128.76 and 45.13 is: 67.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.72 : 128.76 = 45.13 : x
  2. Step 2: Convert to fraction form
    85.72/128.76 = 45.13/x
  3. Step 3: Cross multiply
    85.72x = 128.76 × 45.13
  4. Step 4: Simplify right side
    85.72x = 5,810.94
  5. Step 5: Solve for x
    x = 5,810.94/85.72
  6. Step 6: Final answer
    x = 67.79

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.