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Finding the Fourth Proportional to 1,120.40, 1,680 and 389.76

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Solution

The fourth proportional to 1,120.40, 1,680 and 389.76 is: 584.43

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,120.40 : 1,680 = 389.76 : x
  2. Step 2: Convert to fraction form
    1,120.40/1,680 = 389.76/x
  3. Step 3: Cross multiply
    1,120.40x = 1,680 × 389.76
  4. Step 4: Simplify right side
    1,120.40x = 654,796.80
  5. Step 5: Solve for x
    x = 654,796.80/1,120.40
  6. Step 6: Final answer
    x = 584.43

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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.