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Finding the Fourth Proportional to 781.07, 1,172.21 and 391.46

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Solution

The fourth proportional to 781.07, 1,172.21 and 391.46 is: 587.49

Step by Step Solution

  1. Step 1: Write the proportion equation
    781.07 : 1,172.21 = 391.46 : x
  2. Step 2: Convert to fraction form
    781.07/1,172.21 = 391.46/x
  3. Step 3: Cross multiply
    781.07x = 1,172.21 × 391.46
  4. Step 4: Simplify right side
    781.07x = 458,865.51
  5. Step 5: Solve for x
    x = 458,865.51/781.07
  6. Step 6: Final answer
    x = 587.49

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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.