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Finding the Fourth Proportional to 781.64, 1,172.35 and 391.49

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Solution

The fourth proportional to 781.64, 1,172.35 and 391.49 is: 587.18

Step by Step Solution

  1. Step 1: Write the proportion equation
    781.64 : 1,172.35 = 391.49 : x
  2. Step 2: Convert to fraction form
    781.64/1,172.35 = 391.49/x
  3. Step 3: Cross multiply
    781.64x = 1,172.35 × 391.49
  4. Step 4: Simplify right side
    781.64x = 458,963.30
  5. Step 5: Solve for x
    x = 458,963.30/781.64
  6. Step 6: Final answer
    x = 587.18

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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.