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Finding the Fourth Proportional to 1,121.28, 1,681.52 and 390.68

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Solution

The fourth proportional to 1,121.28, 1,681.52 and 390.68 is: 585.88

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,121.28 : 1,681.52 = 390.68 : x
  2. Step 2: Convert to fraction form
    1,121.28/1,681.52 = 390.68/x
  3. Step 3: Cross multiply
    1,121.28x = 1,681.52 × 390.68
  4. Step 4: Simplify right side
    1,121.28x = 656,936.23
  5. Step 5: Solve for x
    x = 656,936.23/1,121.28
  6. Step 6: Final answer
    x = 585.88

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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.