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Finding the Fourth Proportional to 660.76, 989.72 and 428.90

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Solution

The fourth proportional to 660.76, 989.72 and 428.90 is: 642.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    660.76 : 989.72 = 428.90 : x
  2. Step 2: Convert to fraction form
    660.76/989.72 = 428.90/x
  3. Step 3: Cross multiply
    660.76x = 989.72 × 428.90
  4. Step 4: Simplify right side
    660.76x = 424,485.42
  5. Step 5: Solve for x
    x = 424,485.42/660.76
  6. Step 6: Final answer
    x = 642.42

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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.