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Finding the Fourth Proportional to 85.57, 128.35 and 72.71

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Solution

The fourth proportional to 85.57, 128.35 and 72.71 is: 109.06

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.57 : 128.35 = 72.71 : x
  2. Step 2: Convert to fraction form
    85.57/128.35 = 72.71/x
  3. Step 3: Cross multiply
    85.57x = 128.35 × 72.71
  4. Step 4: Simplify right side
    85.57x = 9,332.26
  5. Step 5: Solve for x
    x = 9,332.26/85.57
  6. Step 6: Final answer
    x = 109.06

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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.