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Finding the Fourth Proportional to 208.17, 312.18 and 86.40

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Solution

The fourth proportional to 208.17, 312.18 and 86.40 is: 129.57

Step by Step Solution

  1. Step 1: Write the proportion equation
    208.17 : 312.18 = 86.40 : x
  2. Step 2: Convert to fraction form
    208.17/312.18 = 86.40/x
  3. Step 3: Cross multiply
    208.17x = 312.18 × 86.40
  4. Step 4: Simplify right side
    208.17x = 26,972.35
  5. Step 5: Solve for x
    x = 26,972.35/208.17
  6. Step 6: Final answer
    x = 129.57

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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.