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Finding the Fourth Proportional to 1,120.80, 1,680.64 and 390.20

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Solution

The fourth proportional to 1,120.80, 1,680.64 and 390.20 is: 585.11

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,120.80 : 1,680.64 = 390.20 : x
  2. Step 2: Convert to fraction form
    1,120.80/1,680.64 = 390.20/x
  3. Step 3: Cross multiply
    1,120.80x = 1,680.64 × 390.20
  4. Step 4: Simplify right side
    1,120.80x = 655,785.73
  5. Step 5: Solve for x
    x = 655,785.73/1,120.80
  6. Step 6: Final answer
    x = 585.11

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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.