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Finding the Fourth Proportional to 120.57, 180.70 and 86.15

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Solution

The fourth proportional to 120.57, 180.70 and 86.15 is: 129.10

Step by Step Solution

  1. Step 1: Write the proportion equation
    120.57 : 180.70 = 86.15 : x
  2. Step 2: Convert to fraction form
    120.57/180.70 = 86.15/x
  3. Step 3: Cross multiply
    120.57x = 180.70 × 86.15
  4. Step 4: Simplify right side
    120.57x = 15,566.19
  5. Step 5: Solve for x
    x = 15,566.19/120.57
  6. Step 6: Final answer
    x = 129.10

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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.