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Finding the Fourth Proportional to 390.87, 538.53 and 285.78

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Solution

The fourth proportional to 390.87, 538.53 and 285.78 is: 393.74

Step by Step Solution

  1. Step 1: Write the proportion equation
    390.87 : 538.53 = 285.78 : x
  2. Step 2: Convert to fraction form
    390.87/538.53 = 285.78/x
  3. Step 3: Cross multiply
    390.87x = 538.53 × 285.78
  4. Step 4: Simplify right side
    390.87x = 153,901.10
  5. Step 5: Solve for x
    x = 153,901.10/390.87
  6. Step 6: Final answer
    x = 393.74

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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.