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Finding the Fourth Proportional to 428.61, 642.51 and 212.07

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Solution

The fourth proportional to 428.61, 642.51 and 212.07 is: 317.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.61 : 642.51 = 212.07 : x
  2. Step 2: Convert to fraction form
    428.61/642.51 = 212.07/x
  3. Step 3: Cross multiply
    428.61x = 642.51 × 212.07
  4. Step 4: Simplify right side
    428.61x = 136,257.10
  5. Step 5: Solve for x
    x = 136,257.10/428.61
  6. Step 6: Final answer
    x = 317.90

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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.