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Finding the Fourth Proportional to 678.88, 1,017.20 and 389.60

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Solution

The fourth proportional to 678.88, 1,017.20 and 389.60 is: 583.76

Step by Step Solution

  1. Step 1: Write the proportion equation
    678.88 : 1,017.20 = 389.60 : x
  2. Step 2: Convert to fraction form
    678.88/1,017.20 = 389.60/x
  3. Step 3: Cross multiply
    678.88x = 1,017.20 × 389.60
  4. Step 4: Simplify right side
    678.88x = 396,301.12
  5. Step 5: Solve for x
    x = 396,301.12/678.88
  6. Step 6: Final answer
    x = 583.76

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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.