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Finding the Fourth Proportional to 985.12, 1,478.56 and 408.40

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Solution

The fourth proportional to 985.12, 1,478.56 and 408.40 is: 612.96

Step by Step Solution

  1. Step 1: Write the proportion equation
    985.12 : 1,478.56 = 408.40 : x
  2. Step 2: Convert to fraction form
    985.12/1,478.56 = 408.40/x
  3. Step 3: Cross multiply
    985.12x = 1,478.56 × 408.40
  4. Step 4: Simplify right side
    985.12x = 603,843.90
  5. Step 5: Solve for x
    x = 603,843.90/985.12
  6. Step 6: Final answer
    x = 612.96

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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.