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Finding the Fourth Proportional to 720.78, 1,081.16 and 258.56

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Solution

The fourth proportional to 720.78, 1,081.16 and 258.56 is: 387.84

Step by Step Solution

  1. Step 1: Write the proportion equation
    720.78 : 1,081.16 = 258.56 : x
  2. Step 2: Convert to fraction form
    720.78/1,081.16 = 258.56/x
  3. Step 3: Cross multiply
    720.78x = 1,081.16 × 258.56
  4. Step 4: Simplify right side
    720.78x = 279,544.73
  5. Step 5: Solve for x
    x = 279,544.73/720.78
  6. Step 6: Final answer
    x = 387.84

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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.