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Finding the Fourth Proportional to 428.78, 643.16 and 104.15

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Solution

The fourth proportional to 428.78, 643.16 and 104.15 is: 156.22

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.78 : 643.16 = 104.15 : x
  2. Step 2: Convert to fraction form
    428.78/643.16 = 104.15/x
  3. Step 3: Cross multiply
    428.78x = 643.16 × 104.15
  4. Step 4: Simplify right side
    428.78x = 66,981.90
  5. Step 5: Solve for x
    x = 66,981.90/428.78
  6. Step 6: Final answer
    x = 156.22

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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.