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Finding the Fourth Proportional to 86.61, 129.61 and 71

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Solution

The fourth proportional to 86.61, 129.61 and 71 is: 106.25

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.61 : 129.61 = 71 : x
  2. Step 2: Convert to fraction form
    86.61/129.61 = 71/x
  3. Step 3: Cross multiply
    86.61x = 129.61 × 71
  4. Step 4: Simplify right side
    86.61x = 9,201.96
  5. Step 5: Solve for x
    x = 9,201.96/86.61
  6. Step 6: Final answer
    x = 106.25

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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.