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Finding the Fourth Proportional to 661.20, 912 and 398.88

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Solution

The fourth proportional to 661.20, 912 and 398.88 is: 550.18

Step by Step Solution

  1. Step 1: Write the proportion equation
    661.20 : 912 = 398.88 : x
  2. Step 2: Convert to fraction form
    661.20/912 = 398.88/x
  3. Step 3: Cross multiply
    661.20x = 912 × 398.88
  4. Step 4: Simplify right side
    661.20x = 363,778.56
  5. Step 5: Solve for x
    x = 363,778.56/661.20
  6. Step 6: Final answer
    x = 550.18

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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.