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Finding the Fourth Proportional to 208.61, 312.86 and 86.81

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Solution

The fourth proportional to 208.61, 312.86 and 86.81 is: 130.19

Step by Step Solution

  1. Step 1: Write the proportion equation
    208.61 : 312.86 = 86.81 : x
  2. Step 2: Convert to fraction form
    208.61/312.86 = 86.81/x
  3. Step 3: Cross multiply
    208.61x = 312.86 × 86.81
  4. Step 4: Simplify right side
    208.61x = 27,158.03
  5. Step 5: Solve for x
    x = 27,158.03/208.61
  6. Step 6: Final answer
    x = 130.19

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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.