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Finding the Fourth Proportional to 428.59, 642.90 and 140

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Solution

The fourth proportional to 428.59, 642.90 and 140 is: 210.01

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.59 : 642.90 = 140 : x
  2. Step 2: Convert to fraction form
    428.59/642.90 = 140/x
  3. Step 3: Cross multiply
    428.59x = 642.90 × 140
  4. Step 4: Simplify right side
    428.59x = 90,006
  5. Step 5: Solve for x
    x = 90,006/428.59
  6. Step 6: Final answer
    x = 210.01

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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.