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Finding the Fourth Proportional to 208.78, 312.92 and 87

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Solution

The fourth proportional to 208.78, 312.92 and 87 is: 130.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    208.78 : 312.92 = 87 : x
  2. Step 2: Convert to fraction form
    208.78/312.92 = 87/x
  3. Step 3: Cross multiply
    208.78x = 312.92 × 87
  4. Step 4: Simplify right side
    208.78x = 27,224.04
  5. Step 5: Solve for x
    x = 27,224.04/208.78
  6. Step 6: Final answer
    x = 130.40

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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.