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Finding the Fourth Proportional to 428.90, 643.31 and 120.74

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Solution

The fourth proportional to 428.90, 643.31 and 120.74 is: 181.09

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.90 : 643.31 = 120.74 : x
  2. Step 2: Convert to fraction form
    428.90/643.31 = 120.74/x
  3. Step 3: Cross multiply
    428.90x = 643.31 × 120.74
  4. Step 4: Simplify right side
    428.90x = 77,670.03
  5. Step 5: Solve for x
    x = 77,670.03/428.90
  6. Step 6: Final answer
    x = 181.09

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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.