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Finding the Fourth Proportional to 1,120.55, 1,680.77 and 390.20

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Solution

The fourth proportional to 1,120.55, 1,680.77 and 390.20 is: 585.27

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,120.55 : 1,680.77 = 390.20 : x
  2. Step 2: Convert to fraction form
    1,120.55/1,680.77 = 390.20/x
  3. Step 3: Cross multiply
    1,120.55x = 1,680.77 × 390.20
  4. Step 4: Simplify right side
    1,120.55x = 655,826.10
  5. Step 5: Solve for x
    x = 655,826.10/1,120.55
  6. Step 6: Final answer
    x = 585.27

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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.