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Finding the Fourth Proportional to 781.72, 1,172.58 and 691.30

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Solution

The fourth proportional to 781.72, 1,172.58 and 691.30 is: 1,036.95

Step by Step Solution

  1. Step 1: Write the proportion equation
    781.72 : 1,172.58 = 691.30 : x
  2. Step 2: Convert to fraction form
    781.72/1,172.58 = 691.30/x
  3. Step 3: Cross multiply
    781.72x = 1,172.58 × 691.30
  4. Step 4: Simplify right side
    781.72x = 810,604.55
  5. Step 5: Solve for x
    x = 810,604.55/781.72
  6. Step 6: Final answer
    x = 1,036.95

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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.