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Finding the Fourth Proportional to 428.90, 643.29 and 120.76

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Solution

The fourth proportional to 428.90, 643.29 and 120.76 is: 181.12

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.90 : 643.29 = 120.76 : x
  2. Step 2: Convert to fraction form
    428.90/643.29 = 120.76/x
  3. Step 3: Cross multiply
    428.90x = 643.29 × 120.76
  4. Step 4: Simplify right side
    428.90x = 77,680.48
  5. Step 5: Solve for x
    x = 77,680.48/428.90
  6. Step 6: Final answer
    x = 181.12

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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.