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Finding the Fourth Proportional to 781.87, 1,172.19 and 391.67

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Solution

The fourth proportional to 781.87, 1,172.19 and 391.67 is: 587.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    781.87 : 1,172.19 = 391.67 : x
  2. Step 2: Convert to fraction form
    781.87/1,172.19 = 391.67/x
  3. Step 3: Cross multiply
    781.87x = 1,172.19 × 391.67
  4. Step 4: Simplify right side
    781.87x = 459,111.66
  5. Step 5: Solve for x
    x = 459,111.66/781.87
  6. Step 6: Final answer
    x = 587.20

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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.