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Finding the Fourth Proportional to 656.40, 905.85 and 390.87

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Solution

The fourth proportional to 656.40, 905.85 and 390.87 is: 539.41

Step by Step Solution

  1. Step 1: Write the proportion equation
    656.40 : 905.85 = 390.87 : x
  2. Step 2: Convert to fraction form
    656.40/905.85 = 390.87/x
  3. Step 3: Cross multiply
    656.40x = 905.85 × 390.87
  4. Step 4: Simplify right side
    656.40x = 354,069.59
  5. Step 5: Solve for x
    x = 354,069.59/656.40
  6. Step 6: Final answer
    x = 539.41

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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.