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Finding the Fourth Proportional to 120.71, 180.90 and 86.69

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Solution

The fourth proportional to 120.71, 180.90 and 86.69 is: 129.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    120.71 : 180.90 = 86.69 : x
  2. Step 2: Convert to fraction form
    120.71/180.90 = 86.69/x
  3. Step 3: Cross multiply
    120.71x = 180.90 × 86.69
  4. Step 4: Simplify right side
    120.71x = 15,681.32
  5. Step 5: Solve for x
    x = 15,681.32/120.71
  6. Step 6: Final answer
    x = 129.91

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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.