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Finding the Fourth Proportional to 285.61, 428.40 and 80.21

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Solution

The fourth proportional to 285.61, 428.40 and 80.21 is: 120.31

Step by Step Solution

  1. Step 1: Write the proportion equation
    285.61 : 428.40 = 80.21 : x
  2. Step 2: Convert to fraction form
    285.61/428.40 = 80.21/x
  3. Step 3: Cross multiply
    285.61x = 428.40 × 80.21
  4. Step 4: Simplify right side
    285.61x = 34,361.96
  5. Step 5: Solve for x
    x = 34,361.96/285.61
  6. Step 6: Final answer
    x = 120.31

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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.