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Finding the Fourth Proportional to 1,121.67, 1,681.12 and 390.39

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Solution

The fourth proportional to 1,121.67, 1,681.12 and 390.39 is: 585.10

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,121.67 : 1,681.12 = 390.39 : x
  2. Step 2: Convert to fraction form
    1,121.67/1,681.12 = 390.39/x
  3. Step 3: Cross multiply
    1,121.67x = 1,681.12 × 390.39
  4. Step 4: Simplify right side
    1,121.67x = 656,292.44
  5. Step 5: Solve for x
    x = 656,292.44/1,121.67
  6. Step 6: Final answer
    x = 585.10

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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.