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Finding the Fourth Proportional to 1,120.91, 1,680.86 and 390.53

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Solution

The fourth proportional to 1,120.91, 1,680.86 and 390.53 is: 585.63

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,120.91 : 1,680.86 = 390.53 : x
  2. Step 2: Convert to fraction form
    1,120.91/1,680.86 = 390.53/x
  3. Step 3: Cross multiply
    1,120.91x = 1,680.86 × 390.53
  4. Step 4: Simplify right side
    1,120.91x = 656,431.43
  5. Step 5: Solve for x
    x = 656,431.43/1,120.91
  6. Step 6: Final answer
    x = 585.63

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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.