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Finding the Fourth Proportional to 285.78, 428.78 and 139.59

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Solution

The fourth proportional to 285.78, 428.78 and 139.59 is: 209.44

Step by Step Solution

  1. Step 1: Write the proportion equation
    285.78 : 428.78 = 139.59 : x
  2. Step 2: Convert to fraction form
    285.78/428.78 = 139.59/x
  3. Step 3: Cross multiply
    285.78x = 428.78 × 139.59
  4. Step 4: Simplify right side
    285.78x = 59,852.70
  5. Step 5: Solve for x
    x = 59,852.70/285.78
  6. Step 6: Final answer
    x = 209.44

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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.