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Finding the Fourth Proportional to 1,120.86, 1,681.20 and 390.45

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Solution

The fourth proportional to 1,120.86, 1,681.20 and 390.45 is: 585.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,120.86 : 1,681.20 = 390.45 : x
  2. Step 2: Convert to fraction form
    1,120.86/1,681.20 = 390.45/x
  3. Step 3: Cross multiply
    1,120.86x = 1,681.20 × 390.45
  4. Step 4: Simplify right side
    1,120.86x = 656,424.54
  5. Step 5: Solve for x
    x = 656,424.54/1,120.86
  6. Step 6: Final answer
    x = 585.64

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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.