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Finding the Fourth Proportional to 1,121.45, 1,681.76 and 428.09

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Solution

The fourth proportional to 1,121.45, 1,681.76 and 428.09 is: 641.97

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,121.45 : 1,681.76 = 428.09 : x
  2. Step 2: Convert to fraction form
    1,121.45/1,681.76 = 428.09/x
  3. Step 3: Cross multiply
    1,121.45x = 1,681.76 × 428.09
  4. Step 4: Simplify right side
    1,121.45x = 719,937.30
  5. Step 5: Solve for x
    x = 719,937.30/1,121.45
  6. Step 6: Final answer
    x = 641.97

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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.