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Finding the Fourth Proportional to 613.90, 921.30 and 408.40

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Solution

The fourth proportional to 613.90, 921.30 and 408.40 is: 612.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    613.90 : 921.30 = 408.40 : x
  2. Step 2: Convert to fraction form
    613.90/921.30 = 408.40/x
  3. Step 3: Cross multiply
    613.90x = 921.30 × 408.40
  4. Step 4: Simplify right side
    613.90x = 376,258.92
  5. Step 5: Solve for x
    x = 376,258.92/613.90
  6. Step 6: Final answer
    x = 612.90

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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.