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Finding the Fourth Proportional to 1,120.80, 1,680.12 and 390.18

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Solution

The fourth proportional to 1,120.80, 1,680.12 and 390.18 is: 584.89

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,120.80 : 1,680.12 = 390.18 : x
  2. Step 2: Convert to fraction form
    1,120.80/1,680.12 = 390.18/x
  3. Step 3: Cross multiply
    1,120.80x = 1,680.12 × 390.18
  4. Step 4: Simplify right side
    1,120.80x = 655,549.22
  5. Step 5: Solve for x
    x = 655,549.22/1,120.80
  6. Step 6: Final answer
    x = 584.89

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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.