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Finding the Fourth Proportional to 1,121.07, 1,681.07 and 390.56

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Solution

The fourth proportional to 1,121.07, 1,681.07 and 390.56 is: 585.65

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,121.07 : 1,681.07 = 390.56 : x
  2. Step 2: Convert to fraction form
    1,121.07/1,681.07 = 390.56/x
  3. Step 3: Cross multiply
    1,121.07x = 1,681.07 × 390.56
  4. Step 4: Simplify right side
    1,121.07x = 656,558.70
  5. Step 5: Solve for x
    x = 656,558.70/1,121.07
  6. Step 6: Final answer
    x = 585.65

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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.