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Finding the Fourth Proportional to 781.67, 1,172.18 and 391.53

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Solution

The fourth proportional to 781.67, 1,172.18 and 391.53 is: 587.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    781.67 : 1,172.18 = 391.53 : x
  2. Step 2: Convert to fraction form
    781.67/1,172.18 = 391.53/x
  3. Step 3: Cross multiply
    781.67x = 1,172.18 × 391.53
  4. Step 4: Simplify right side
    781.67x = 458,943.64
  5. Step 5: Solve for x
    x = 458,943.64/781.67
  6. Step 6: Final answer
    x = 587.13

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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.