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Finding the Fourth Proportional to 85.74, 128.60 and 54.47

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Solution

The fourth proportional to 85.74, 128.60 and 54.47 is: 81.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.74 : 128.60 = 54.47 : x
  2. Step 2: Convert to fraction form
    85.74/128.60 = 54.47/x
  3. Step 3: Cross multiply
    85.74x = 128.60 × 54.47
  4. Step 4: Simplify right side
    85.74x = 7,004.84
  5. Step 5: Solve for x
    x = 7,004.84/85.74
  6. Step 6: Final answer
    x = 81.70

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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.