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Finding the Fourth Proportional to 428.22, 642.30 and 139.66

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Solution

The fourth proportional to 428.22, 642.30 and 139.66 is: 209.48

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.22 : 642.30 = 139.66 : x
  2. Step 2: Convert to fraction form
    428.22/642.30 = 139.66/x
  3. Step 3: Cross multiply
    428.22x = 642.30 × 139.66
  4. Step 4: Simplify right side
    428.22x = 89,701.49
  5. Step 5: Solve for x
    x = 89,701.49/428.22
  6. Step 6: Final answer
    x = 209.48

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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.