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Finding the Fourth Proportional to 390.78, 539.52 and 280.17

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Solution

The fourth proportional to 390.78, 539.52 and 280.17 is: 386.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    390.78 : 539.52 = 280.17 : x
  2. Step 2: Convert to fraction form
    390.78/539.52 = 280.17/x
  3. Step 3: Cross multiply
    390.78x = 539.52 × 280.17
  4. Step 4: Simplify right side
    390.78x = 151,157.32
  5. Step 5: Solve for x
    x = 151,157.32/390.78
  6. Step 6: Final answer
    x = 386.81

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.